Studies may be focused at the regional scale, investigating the tectonic setting responsible for and controlling volcanic activity, both along divergent and convergent plate boundaries, as well in intraplate settings. At a more local scale, all types of surface deformation in volcanic areas are of interest, such as elastic inflation and deflation, or anelastic processes, including caldera and flank collapses. Deeper, sub-volcanic deformation studies, concerning the emplacement of intrusions, as sills, dikes and laccoliths, are most welcome. We also particularly welcome geophysical data aimed at understanding magmatic processes during volcano unrest. These include geodetic studies obtained mainly through GPS and InSAR, as well as at their modelling to imagine sources.
The session includes, but is not restricted to, the following topics:
• volcanism and regional tectonics;
• formation of magma chambers, laccoliths, and other intrusions;
• dyke and sill propagation, emplacement, and arrest;
• earthquakes and eruptions;
• caldera collapse, resurgence, and unrest;
• flank collapse;
• volcano deformation monitoring;
• volcano deformation and hazard mitigation;
• volcano unrest;
• mechanical properties of rocks in volcanic areas.
Orals: Mon, 4 May, 08:30–15:45 | Room K2
The emplacement of intrusions (e.g., sills, dikes, laccoliths) is a key process shaping the structural evolution of passive continental margin basins, and their emplacement characteristics are crucial for understanding magmatism-driven deformation of the basin fillings. This study focuses on the intrusion emplacement characteristics in a passive continental margin basin offshore southern Brazil, aiming to elucidate the spatiotemporal patterns of intrusions and their genetic links with the stratigraphic evolution of the basin.
We integrated 3D seismic data with multi-disciplinary datasets from drilled boreholes, including petrophysical, geochronological, and petrographic information. A comprehensive interpretation approach was adopted, incorporating insights from structural geology, stratigraphy, and volcanology to construct a unified model for intrusion emplacement and its coupling relationship with basin filling evolution.
Seismic interpretation reveals that igneous intrusions (sills, dikes, laccoliths) in the study area exhibit distinct high-amplitude responses on seismic profiles, which facilitates the identification of their geometric shapes and spatial distributions—key characteristics of intrusion emplacement. The emplacement of these intrusions induced significant uplift and arching of pre-eruptive strata in the sub-volcanic zone. By analyzing the spatiotemporal patterns of sedimentary filling, variations in sedimentary thickness, the spatial location of volcanic craters, and the relationship between sedimentary rocks and intrusions beneath volcanic cones, we successfully constrained the emplacement period of intrusions, the process of basin subsidence, and the active period of magmatism. Additionally, multiple types of sediment-magma interactions were identified, which further reflect the response of sedimentary systems to intrusion emplacement and provide supplementary evidence for understanding emplacement characteristics.
This study systematically clarifies the intrusion emplacement characteristics of the passive continental margin basin in offshore southern Brazil, providing critical insights into the mechanisms of intrusion emplacement in similar geological settings. It also offers a valuable reference for understanding magmatism-driven basin filling evolution in global passive continental margin basins.
How to cite: Yang, X.: Intrusion Emplacement Characteristics of the Passive Continental Margin Basin, Offshore Southern Brazil, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4940, https://doi.org/10.5194/egusphere-egu26-4940, 2026.
The build-up of magma beneath a volcano can be revealed by ground surface deformation, and the recorded surface displacement can be modelled to infer details of the magma system dynamics. Constraints on magmatic processes can then be used to aid hazard assessment and eruption forecasting. However, inferring the processes occurring in the magma plumbing system during volcano deformation episodes is inherently dependent on the modelling approach used to interpret the recorded deformation data, and in particular the choices of rheology used to represent the solid and fluid parts of the magmatic and host rock system. Here, we explore the elastic, viscoelastic, and poroelastic rheologies typically implemented in volcano deformation analyses, and assess how their choices impact the interpretation of recorded volcano deformation data. Different viscoelastic rheologies can produce drastically different predicted surface deformation patterns, but all viscoelastic rheologies will typically lead to different source pressurisation estimates compared to a linear elastic rheology. Poroelastic source implementations can produce surface deformation even after supply to a reservoir has stopped, due to diffusive redistribution of pore pressures. Both viscous and poroelastic processes add a time-dependent component to the stress-strain evolution, which changes model predictions of temporal volcano deformation. Consequently, when applied to interpret recorded deformation, viscous and poroelastic rheologies can suggest non-linear magma system dynamics that are not captured by a simpler purely elastic model rheology. Issues persist with reliably parameterising different rheological approaches but their importance in modifying surface deformation predictions cannot be overlooked.
How to cite: Hickey, J., Alshembari, R., Current, G., Gregg, P., Head, M., Mantiloni, L., and Zhan, Y.: Rheological effects in volcano deformation modelling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11297, https://doi.org/10.5194/egusphere-egu26-11297, 2026.
Soufrière Hills is an active dome building volcano on the island of Montserrat, part of the Eastern Caribbean, that has been in a state of ongoing eruption since 1995. Multi-parametric monitoring is conducted by the Montserrat Volcano Observatory, including an island-wide ground deformation GNSS network operating for nearly three decades. The ground displacement timeseries has been key to modelling the subsurface processes and pressure changes causing them, often using a pressurized cavity or, in more recent models, a poroelastic body in an elastic medium. However, a purely magmatic deformation source has thus far been unable to fully account for the observed deformation signal across the island, leading to significant residuals between simulated and observed geodetic data, particularly at sites closest to the vent. In this study, we will investigate the influence of the Soufrière Hills hydrothermal system on the deformation field. Fumarolic fields and heated springs suggest the presence of an active hydrothermal system at high elevations near the volcanic vent. In the southwest, a more distal geothermal upwelling, as well as anomalies in seismic tomography and gravity data, suggests the presence of a deeper accumulation of hydrothermal fluids, hypothesised to have formed due to the intersection of a number of regional faults and zones of weakness.
In this study we compare magmatic, hydrothermal, and combined deformation source simulations to investigate how different causal mechanisms influence the modelled surface displacement field across Montserrat. We use observed deformation from Montserrat between 2010 and 2022 via GNSS records from 14 continuous monitoring stations to validate our models. Two different model setups are tested: a homogeneous model as a computationally inexpensive baseline, and a heterogeneous model containing seismically defined low permeability andesitic cores in the north of the island, faults in the southwest, and a clay capped region of high permeability in the region of the inferred hydrothermal aquifer. Deviating from traditional volcano-deformation models, our models include a seismically inferred magma reservoir geometry in a poroelastic model domain in an effort to better simulate observed deformation at near-vent GNSS stations. The results from this study will assist volcanic hazard assessment and contribute to the investigation of on-island geothermal resources.
How to cite: Dibben, J., Hickey, J., Geyer, A., Pascal, K., and Ryan, G.: Modelling volcanic deformation from coupled magmatic and hydrothermal systems; application to Soufrière Hills Volcano, Montserrat, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10568, https://doi.org/10.5194/egusphere-egu26-10568, 2026.
Semeru volcano, located in eastern Java, Indonesia, reactivated in December 2021 following the destabilization of a
summit lava dome that had been growing since 2009. Monitoring topographic changes and surface deformation at
Semeru is important for understanding eruptive processes and assessing associated hazards, but remains challenging
due to the inaccessibility of the summit area, frequent activity, and the cost and sparsity of ground-based instrumentation.
In this context, satellite remote sensing combining bi-static and repeat-pass Synthetic Aperture Radar interferometry
(InSAR) with high resolution optical photogrammetry provides observations of surface deformation and topographic
changes at high spatial resolution. However, steep topography, tropical climate, dense vegetation, and rapidly evolving
volcanic deposits strongly affect InSAR observations introducing noise associated with atmospheric delays, temporal
decorrelation, and residual topographic errors. These external contributions can obscure low-amplitude deformation
signals, especially during periods of moderate or persistent activity. A set of seven high-resolution digital elevation
models (DEMs) is produced from TanDEM-X bistatic acquisitions and Pleiades stereo images. These DEMs allow
detailed characterization of the summit dome and proximal deposits prior and posterior to the December 2021 eruption.
Between 2015 and July 2021, the lava dome grew heterogeneously, reaching a volume of about 1.35 million m3. Over
the same period, and pyroclastic deposits accumulated with thicknesses locally exceeding 75 m, progressively filling
existing eastward channels and contributing to a redirection of eruptive activity toward the eastern flank after 2018.
The major 2021 eruptions produces a large pyroclastic density current reshaping the summit and the Besuk Kobokan
valley with a total volume of material mobilized during the eruption of 29.1 Mm3. The analysis of ground deformation
using TerraSAR-X InSAR data, corrected for atmospheric delays using ERA-5 reanalysis, reveals spatially coherent
patterns of subsidence affecting older lava flows and pyroclastic deposits on the southeastern flank of Semeru. These
signals are interpreted as post-emplacement compaction, with line-of-sight displacement rates of 5 cm/yr. However,
low and spatially variable interferometric coherence within the summit crater and the main deposition channel prevents
reliable measurement of post-eruptive magmatic deformation in these areas. Volcanoes capable of rapid transitions from
Strombolian to Plinian activity in tropical environments affected by intense rainfall, as observed at Semeru in December
2021, remain hazardous and insufficiently understood, highlighting the need for long-term, integrated monitoring of both
topographic changes and ground deformation to better characterize eruptive processes and associated hazards.
How to cite: Albino, F., Bouygues, P., and Pinel, V.: Characterization of activity at Semeru volcano using high resolution radar and optical imagery, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10915, https://doi.org/10.5194/egusphere-egu26-10915, 2026.
The joint analysis and interpretation of multiparameter datasets from active volcanoes may lead to misleading conclusions, if important factors are not appropriately considered. Among these, magma compressibility, which is mainly controlled by the volume fraction of exsolved gas in the magma, may play a key role.
Past studies showed that the intrusion of new magma in a shallow reservoir may lead to significant mass increase without the expected volume change, since magma compressibility buffers most of the chamber expansion. Similarly, the magma chamber volume reduction during an eruptive phase may be much lower than the volume of erupted material, due to pressure-driven gas exsolution and expansion, compensating the withdrawal of magma, thus buffering the contraction of the reservoir.
Here, we introduce a theoretical study on how the different compressibility of the magma at different depths (variable amount of exsolved volatiles in equilibrium with the silicate melt) may influence the patterns of deformation and gravity changes observed at the surface. Magma intruding a volcano’s plumbing system may induce heterogeneous responses across different depths. At deeper levels, where magma compressibility is lowest, volume change may be substantial and control most of the observed ground deformation. Conversely, at shallower levels, where magma compressibility is highest, important mass changes may develop with only minor volume changes, accounting for most of the gravity changes observed at the surface.
An important broader implication is that ground deformation and gravity data may not be suitably modelled by assuming a single, uniform source. Rather, a vertically distributed and mechanically heterogeneous magma system may need to be considered. This underscores the need for a joint interpretation of deformation, gravity, and volatile content data when investigating volcanic processes.
How to cite: Carbone, D., Liuzzo, M., Beauducel, F., and Rivalta, E.: Magma compressibility matters: a key to decoding multiparameter datasets from active volcanoes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5204, https://doi.org/10.5194/egusphere-egu26-5204, 2026.
In January 2025, Santorini and its neighbouring islands experienced an intense earthquake swarm, prompting the Greek authorities to declare a state of emergency followed by the island’s evacuation of the majority of the population. Following a gradual inflation and rise in seismic activity beneath the Santorini caldera, the main seismic swarm began on January 27, close to the submarine volcano Kolumbo, 10 km offshore NE of Santorini at 18 km depth. The Santorini and Kolumbo volcanoes have both produced highly explosive (VEI 5) eruptions in historical times, including the 1650 eruption of Kolumbo, which formed a 2.5 km-wide and 500 m-deep submarine crater and triggered a tsunami that devastated the surrounding islands. Although petrological, seismological, and geodetic analyses identified distinct shallow- and mid-crustal magma reservoirs, there has been debate over whether the two volcanic centres are connected and share a common deep magma source, or whether they result from distinct plumbing systems. The 2025 seismic crisis provided an unprecedented opportunity to observe the volcanic system and investigate the potential deep coupling. Integrating seismic and geodetic data from onshore and offshore instruments, we observe and model the dynamic emplacement of a 13-km long intrusion with a volume of 0.31 km3 into the upper crust offshore Santorini, reactivating principal regional faults and arresting 3–5 km below the seafloor. We determine a gradual inflation of Santorini's shallow reservoir 6 months before the crisis, during the intrusion a mid-crustal reservoir beneath Kolumbo at ~7.6 km depth rapidly deflated. This suggests that both volcanoes share, and potentially compete for, a common deep magma supply. In December 2025, we recovered additional ocean-bottom seismometers and pressure sensors, enabling us to refine our seismological catalogues and deformation modelling during and after the seismic crisis. Our analyses highlight the importance of shoreline-crossing monitoring and the need for real-time access to submarine sensor data for a more robust crisis response.
How to cite: Karstens, J., Isken, M. P., Nomikou, P., Parks, M. M., Hooft, E. E. E., Anastasiou, D., Shapiro, N. M., Walter, T. R., Rivalta, E., Kopp, H., Dahm, T., Berndt, C., Drouin, V., and Blanch Jover, M.: Shared magma supply at Santorini and Kolumbo constrained by amphibious seismological and geodetic analyses of the 2025 dike intrusion, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12425, https://doi.org/10.5194/egusphere-egu26-12425, 2026.
At active volcanoes, surface deformation and seismicity reflect underlying processes related to regional tectonics as well as the storage and movement of magma and fluids. These processes frequently overlap, complicating efforts to distinguish between magmatically, hydrothermally, and tectonically driven volcanic unrest. As a result, interpreting unrest signals remains a major challenge in volcanology, particularly if geophysical and geodetical observations are not integrated with physics-based models. In this study, we investigate the subsurface processes that may account for the pulsating seismicity observed along a ~30km-long NE-SW-trending structure during the 2025 Santorini-Amorgos (Greece) earthquake crisis, using physics-based, time-dependent Finite Element Method (FEM) models. Specifically, we simulate crustal extension and poroelastic deformation driven by magmatic and/or hydrothermal pressure sources. Our preliminary results show that the pulsating seismic patterns observed during the seismic crisis may have been controlled by a transient poroelastic response of the shallow crust to the transport of volatiles from a deep magma reservoir to the surface. Numerical simulations show that the sudden pressurization of leaky magma reservoirs, which release fluids through permeable pathways, generates cyclic and laterally migrating zones of tensile stress within a depth-dependent, highly fractured elastic crust. This dynamic response contrasts with the more localized and static stress accumulation produced by the pressurization of sealed magma reservoirs, thus underscoring the critical role of fluid migration in controlling the spatial and temporal evolution of seismicity during volcanic unrest. Integrating fluid–rock coupling into models of fluid transport and crustal pressurization offers a pathway toward more reliable interpretation of unrest signals and improved volcanic hazard assessments.
How to cite: Drymoni, K., Girona, T., Pesicek, J., Prejean, S., Lundgren, P., Kendrick, J., and Lavallée, Y.: Investigating the subsurface drivers of the 2025 Kolumbo volcano-tectonic unrest , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11169, https://doi.org/10.5194/egusphere-egu26-11169, 2026.
Since late summer of 2024 the Santorini Volcanic Complex (SVC) in South Aegean Sea (Greece) entered another phase of unrest as GNSS data indicated the start of strong deformation onshore Thera Island followed by increased seismic activity, offshore, NE of the island in late January 2025. The seismic events were detected first inside the caldera (September 2024 to early 2025), then spreading with intense activity towards the north-east to Anydros Islet, spanning an overall distance of ~30 km, displaying a NE-SW orientation. The seismicity pattern indicated swarm characteristics that culminated during February 2025, and subsequent seismic activity declined but remained above the unrest levels during the rest of 2025. In terms of ground deformation, cm to dm-size displacements were recorded onshore Thera and in neighbouring islands during the period August 2024 - February 2025. In early 2025 several groups installed new permanent GNSS equipment on Thera and surrounding islands. This GNSS instrumentation in South Cyclades reached 32 sites during April 2025. Those stations provide a wealth of open data that we use to study the evolution of the deformation in the broad South Cyclades Islands.
Overall, the GNSS data showed an inflation of the Thera volcano since August 2024. The modelled magma source was located near the inflation centre of 2011-2012 unrest period. At the end of February 2025, the ground displacements in South Cyclades islands depicted a NE-SW converging pattern between Thera and Anydros, and a NW-SE diverging pattern between Ios-Naxos and Astypalaia Islands. The motion amplitudes were large, exceeding 13 cm at Thera and 3 cm at Naxos. The February 2025 GNSS data fits well with a dislocation model of a south-east dipping fault located between the Kolumbo submarine volcano and the Anydros islet (Briole et al. 2025). Since March 2025, the deformation continues with the positive, 3D baseline rate changes between GNSS stations exceeding the pre-unrest rates thus indicating a nearly-aseismic opening of the Santorini – Amorgos graben. This implies that new magma continues to arrive at shallow crustal depths.
Briole, P., Ganas, A., Serpetsidaki, A., Beauducel, F., Sakkas, V., Tsironi, V., Elias, P. 2025. Volcano-tectonic interaction at Santorini. The crisis of February 2025. Constraints from geodesy, Geophysical Journal International, ggaf262, https://doi.org/10.1093/gji/ggaf262
How to cite: Ganas, A., Sakkas, V., Bonforte, A., Vernant, P., Briole, P., Liadopoulos, E., Consoli, S., Doerflinger, E., Madonis, N., Mintourakis, I., and Goutsos, G.: GNSS data highlight new spatial and temporal dimensions of the Santorini volcano-tectonic unrest during 2025, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15028, https://doi.org/10.5194/egusphere-egu26-15028, 2026.
Caldera collapse or resurgence is commonly accommodated by slip along a near-cylindrical ring fault system, and is hence often idealized as a rigid piston moving in response to pressure changes in a fluid chamber. Existing piston models explore variations in geometry and mechanical properties of the reservoir and ring fault, but they generally neglect effects of regional tectonic stresses and pore-fluid pressures. Here we present a new analytical piston model that incorporates the regional stress state as a single parameter, the “average earth pressure coefficient,” which is defined as the mean horizontal to vertical effective stress. The presence of pore-fluids is incorporated by using Terzaghi’s effective stress principle, which governs the effective normal stress acting on the ring fault. Data from 14 active caldera volcanoes that have well-constrained piston dimensions and that span a range of eruptive compositions and collapse magnitudes are used to explore realistic model parameter ranges.
The model results are captured by a dimensionless stability parameter (μK/r̄), combining effective ring fault friction (μ), average earth pressure coefficient (K), and piston radius normalized by its thickness (r̄). This parameter governs piston stability and describes a hysteresis (i.e., a history-dependent lag) between changes in magma reservoir pressure and ring-fault slip. A key finding is that extensional tectonic stresses, low ring-fault friction, and/or elevated pore-fluid pressures are necessary conditions for initiating caldera collapse and resurgence, particularly at calderas with high thickness to diameter (T/D) ratios. Consistent with model predictions, most of the well-constrained calderas examined here occur in extensional or transtensional tectonic settings; collapse or resurgence under a compressional tectonic regime is comparatively rare.
How to cite: Woodell, D., Schöpfer, M., and Holohan, E.: Influence of tectonic stress and pore-fluid pressure on caldera collapse and resurgence – a 3D analytical solution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13925, https://doi.org/10.5194/egusphere-egu26-13925, 2026.
Kīlauea’s 2018 collapse represents one of the best-monitored caldera-forming events recorded. A dense network of geodetic and seismic instrument, complimented by still and satellite-based imagery, captured the full temporal evolution of summit deformation and clearly defined distinct collapse phases. An initial pre-collapse phase was characterised by lava-lake drainage and small, elastic surface displacements, followed by a three non-elastic collapse phases, captured on GNSS stations NPIT and CALS. This detailed and well-resolved, multiphase evolution makes Kīlauea an exceptional case for testing mechanical models of caldera collapse.
Analytical and continuum-based numerical models are commonly used to relate these surface displacements to deformation sources at depth. However, their elastic or viscoelastic material assumptions limit the representation of large-strain discontinuous deformation, such as fracturing and faulting, typical of caldera collapse events. To overcome this, we use 3D Discrete Element Method (DEM) modelling, in conjunction with Finite Volume Method (FVM), to capture a transition from elastic to non-elastic (fictional-plastic) behaviour similar to that during the 2018 Kīlauea collapse event.
Sentinel-1 acquisitions between the 5th and 14th of May 2018 were used to compute surface displacements during the elastic, pre-collapse subsidence phase. The resulting summit subsidence provided constraints on subsurface source characteristics and were used to test a range of chamber geometries, depths and pressure states using FVM models. This approach allowed for a rapid and systematic exploration of the trade-offs among these parameters and demonstrates the non-unique elastic surface displacement solutions, consistent with the observed elastic, pre-collapse deformation at Kīlauea.
The “best-fitting” parameter combinations were then used to inform forward modelling within the 3D DEM solutions. The initial source geometry, as constrained by FVM models, had a depth of 500m, vertical axis of 2000m and horizontal axes of 1500m. As underpressure was progressively increased to 6-8 MPa, deformation transitioned from elastic into non-elastic, as characterised by host-rock fracturing and accelerated summit subsidence. The DEM model subsidence curve mimics closely that measured by GNSS at Kīlauea. Furthermore, model fracture population characteristics through time show similarly with observed earthquake magnitude distributions. This study thus highlights the capacity of 3D DEM models for capturing structural, geodetic and seismic observations during large-strain discontinuous events at volcanoes.
How to cite: Austin, T., Harnett, C., Holohan, E., Hrysiewicz, A., and Schöpfer, M.: Modelling the 2018 Kīlauea Caldera Collapse with a joint Finite Volume Method and Distinct Element Method approach, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21028, https://doi.org/10.5194/egusphere-egu26-21028, 2026.
Kīlauea volcano, on the Island of Hawaiʻi, is one of the most active volcanoes on Earth. Eruptive activity alternates between the summit caldera and two rift zones, to the east and southwest. On June 3, 2024, Kīlauea experienced its first eruption along the Southwest Rift Zone (SWRZ) in 50 years. This brief eruption was preceded by multiple seismic swarms, some associated with dike intrusions, that started in November 2023. These dikes did not reach the surface but reactivated pre-existing faults and generated new structures, reshaping the rift’s near-surface deformation patterns.
To quantify these surface changes, we used high-resolution topographic datasets derived from our helicopter photogrammetry surveys conducted in April 2022 and September 2024. These campaigns produced centimeter-scale DEMs (~8 cm) and orthomosaics (~4 cm), enabling detailed mapping of newly formed fractures, vertical offsets, and extensional opening across the ~12 × 2 km study area. To expand spatial coverage and better constrain multi-year deformation patterns, we complemented these products with airborne LiDAR acquisitions from missions in July 2019 and September 2024. The integration of these multi-temporal topographic datasets reveals the subtle and rapid morphological changes associated with magma intrusion and fault reactivation.
To better understand the kinematics of fault reactivation and magma propagation, we integrated these structural observations with seismic data recorded before, during, and after the June 2024 eruption. This approach reveals the along-rift migration of magma from the summit reservoir, its interaction with pre-existing faults, and the formation of new surface structures. Our analyses highlight the role of flank instability in controlling both rift dynamics and surface faulting during the eruptive episode.
By merging LiDAR, photogrammetry, InSAR, and seismic datasets, this study demonstrates a multi-method approach for capturing near-field deformation with unprecedented detail. Our analysis provides new insights into the mechanics of magma-driven faulting, the propagation of eruptive activity along rift zones, and the interplay between shallow and deep processes. These results not only enhance the fundamental understanding of volcanic rifting dynamics but also inform the development of more accurate hazard monitoring and forecasting models, offering practical applications for risk assessment and mitigation at Kīlauea and similar rift-controlled volcanic systems worldwide.
This study illustrates how integrating multi-temporal, high-resolution geospatial datasets with geophysical observations can advance both scientific knowledge and hazard management strategies. Our approach provides a framework for future eruptions, enabling rapid detection of surface deformation, tracking of magma pathways, and improved preparedness for volcanic crises.
How to cite: Mannini, S., Ruch, J., Lundblad, S., Oestreicher, N., Hazlett, R., Downs, D., Zoeller, M., Chang, J., and Johanson, I.: High-resolution monitoring techniques for fault reactivation during the 2024 Kīlauea Southwest Rift Zone eruption, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-810, https://doi.org/10.5194/egusphere-egu26-810, 2026.
Kīlauea, Hawaii, one of the world's most active volcanoes, has experienced 40 episodic eruptions (at the time of writing) with remarkable lava fountain heights in Halemaʻumaʻu Crater since December 2024. Following a dike intrusion and successive opening of a conduit to the surface within the Halemaʻumaʻu crater on December 23rd 2024, the eruption episodes entered a stable pattern from January 2025 onwards, consisting of ~hours-long lava fountain events separated by days-to-weeks long repose periods. Lava fountaining events have reached heights of 450 m and all lava flows to date have been confined to Halemaʻumaʻu crater.
We study this outstanding eruption sequence with a combination of seismic and geodetic data analyses to understand how melt moves through Kīlauea’s plumbing system and how the system has evolved over time. We estimate the location of seismic tremor, which is the most dominant seismic signal of this eruption sequence, to study the eruption dynamics and inter-eruptive recharge of magma reservoirs. We also examine relative changes in frequency (df/f) and seismic velocity (dv/v), as well as tilt, GNSS and InSAR data. Taken together, these data allow us to study the geophysical response to the eruption dynamics in close detail.
We infer that the current eruptions are controlled by a complex subsurface magma plumbing system with migrating melt sources. We derive three distinct phases of activity which show the subsequent deflation of a shallow and then deeper magma reservoir, as well as melt recharge from depth and the dynamics of the shallow reservoir controlling the lava fountaining. Our study sheds light on the dynamics between different magma reservoirs and links to surface processes. It further showcases how tremor locations could be used, in combination with seismic velocity changes, to track melt movement in near-real time in the future.
How to cite: Reiss, M. C., Caudron, C., Sens-Schönfelder, C., Jolly, A. D., Roman, D. D., Wauthier, C., Lo, A. W. K., Anderson, K., and Flinders, A.: The 2024-2026 Kīlauea eruption sequence: eruption patterns, magma source migration and the evolution of the plumbing system, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9963, https://doi.org/10.5194/egusphere-egu26-9963, 2026.
Phases of accelerated normal faulting in the Taupō Volcanic Zone have been demonstrated to be triggered by rhyolite eruptions, yet little is known about how the Taupō Fault Belt responds in the aftermath of caldera-forming events, particularly the 232 CE Taupō eruption. To address this issue, we conducted paleoseismic trenching coupled with remote and field analyses of the Whakaipō Fault (north Taupō) and the displaced post-232 CE paleoshorelines intersected by this structure. The throw profiles along the Whakaipō Fault reveal increasing throw in proximity to Lake Taupō, highlighting the importance of Taupō volcano (in particular the 232 CE caldera margin) for localising fault strain. Paleoseismic trenching exposed a ~50º dipping un-degraded paleoscarp draped by fall deposits of the 232 CE eruption, implying that fault slip occurred in the days to months preceding the eruption. Analysis of fault and paleoshoreline displacements at Whakaipō Bay on the northern shoreline of Lake Taupō suggest that two main phases of slip on the Whakaipō Fault occurred: (1) an “aftermath” phase, occurring over a ~10-20-year period after the 232 CE eruption, during which 5-10 m of throw was accrued locally on the fault; and (2) a subsequent “longer-term” phase through to the present day, during which 2.8 ± 0.3 m of fault throw has accrued. Faulting during the aftermath phase is estimated to account for ~75% of the total extension accommodated locally on the Whakaipō Fault since 232 CE, and demonstrates that exceptionally large (>5 m) normal fault displacements may accrue along the Taupō Fault Belt in association with caldera-forming eruptions.
How to cite: Muirhead, J., Gold, A., Snowden, M., Villamor, P., Wilson, C., Coffey, G., and Morgenstern, R.: Large-scale rift-related faulting linked to a caldera-forming eruption: A case study from Taupō, New Zealand, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1601, https://doi.org/10.5194/egusphere-egu26-1601, 2026.
Campi Flegrei caldera (Italy) has experienced repeated unrest episodes over historical and instrumental times, with the latest Monte Nuovo eruption in 1538 CE, making eruption forecasting particularly challenging. This contribution integrates long-term records of surface deformation with modern geodetic observations to interpret the short- and long-term dynamics of the caldera over the last 5000 years. A revised dataset of 32 elevation points integrates onshore borehole stratigraphy and offshore abrasion platforms, and provides documentation of the uplift due to the resurgence in the centre of the caldera 5 ka. Also, historical, archaeological, and bathymetric data constrain elevation changes at 20 coastal sites since Roman times, allowing reconstruction of pre-, syn-, and post-eruptive deformation associated with the Monte Nuovo eruption. Then, GNSS and InSAR measurements documenting the unrest since 2005 are combined with 3D finite element modelling to infer the geometry, depth, and volume changes of the active plumbing system. Results over these different time periods consistently indicate an active two-source plumbing system at Campi Flegrei, comprising a shallow deformation source at ~4–5 km depth beneath Pozzuoli and a deeper magmatic reservoir at ~8 km depth. Similar deformation patterns and source configurations characterize both historical eruptive phases and the current unrest. Petrological constraints suggest that magma ascent to depths shallower than ~8 km is the primary driver of unrest, even when an eruption does not occur. These findings provide a coherent framework for linking centuries-scale caldera dynamics with present-day observations. They suggest that the magmatic system at Campi Flegrei has been stable over the last 5000 years, thereby improving our understanding of unrest processes at this caldera.
How to cite: Trasatti, E., Astort, A., Polcar1, M., De Martino, P., Caricchi, L., Clark, J. G., Del Gaudio, C., Beccaro, L., Borgstrom, S., Acocella, V., Magri, C., Carlino, S., Pivetta, T., Riccardi, U., Ricco, C., Galetto, F., and Di Vito, M. A.: Surface deformation and volcanic activity at Campi Flegrei caldera (Italy) over the last 5000 years, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9062, https://doi.org/10.5194/egusphere-egu26-9062, 2026.
Following a quiescent period of 3,000 years and several centuries of subsidence, with only one eruption in 1538, Campi Flegrei has experienced intermittent unrest since 1950. The 1982-84 uplift episode was followed by a period of subsidence, but since the early 2000s there has been almost continuous uplift, accompanied by geochemical anomalies and seismicity. In 2012, the Major Risk Commission raised the Alert Level from green to yellow.
SAR images from different missions have made it possible to monitor the deformation field of Campi Flegrei since the 1990s. In particular, the periods 1993–2010 and 2015–present have been covered by the ERS/ENVISAT and Sentinel-1 missions of ESA, respectively. The time gap between these two periods has recently been filled using Radarsat-2 images (Amoruso et al. 2025). Consequently, we were able to conduct a systematic analysis of Campi Flegrei deformation over the last three decades. We have employed linear regression models and blind source separation techniques (Principal Component Analysis and Independent Component Analysis).
The preliminary results suggest the coexistence of two stationary deformation fields throughout the entire investigated period. The field with the larger amplitude has dimensions similar to those of the caldera, and its temporal history is almost the same as that of the area of maximum uplift. This field is consistent with a pressurised sill located around 4 km deep. The other field is less conspicuous, but it may have even more significant implications. It is more extensive, it is shifted eastwards relative to the centre of the caldera, it is characterised by uplift since at least the beginning of the available DInSAR time series, and it is consistent with a deep pressurised deformation source. In addition, anomalies in the Solfatara area (Amoruso et al. 2014) and in the Accademia Aeronautica area (Giudicepietro et al. 2024) are confirmed and detailed. In this way, the deformation of Campi Flegrei is fully satisfied within data uncertainties throughout the entire period under investigation.
References
Amoruso, A. et al., J. Geophys. Res. Solid Earth, 119, 858–879, 2014.
Amoruso, A. et al., Remote Sens., 17, 3268, 2025.
Giudicepietro, F., et al., Int. J. Appl. Earth Obs. Geoinf., 132, 104060, 2024.
How to cite: Amoruso, A. and Crescentini, L.: DInSAR data from the last three decades reveals persistent large-scale features and local anomalies in the ground deformation of Campi Flegrei, Italy., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17598, https://doi.org/10.5194/egusphere-egu26-17598, 2026.
On 1 September 2025, an Md 4.0 earthquake occurred within a seismic swarm at the Campi Flegrei caldera (Italy) and produced an unprecedented coseismic displacement. The resulting ground deformation, reaching approximately up to 4 cm, clearly outlined the directions of motion of a distinct crustal block and revealed an extensional displacement pattern. This deformation developed in an area where a geodetic anomaly (an uplift deficit, in particular), superimposed on the long-term background deformation field, was identified in previous studies. The spatial distribution and geometry of the deformation, retrieved through GNSS and DInSAR measurements, closely replicate those of the previously recognized anomaly in the Mt. Olibano–Accademia sector, thereby confirming the active involvement of this structural domain in the ongoing caldera dynamics. The sharp and well-defined displacement associated with the Md 4.0 earthquake allowed us to retrospectively identify smaller, analogous deformation episodes that occurred earlier in the unrest sequence but remained less distinct due to their limited amplitude. Altogether, these observations place new constraints on the mechanical behavior of the central–eastern sector of the Campi Flegrei caldera. They improve our understanding of how localized fracturing and faulting processes, within the shallow crust, interact with the broader deformation field driven by the current unrest phase.
How to cite: Macedonio, G., Giudicepietro, F., Casu, F., Bonano, M., Brandi, G., De Luca, C., De Martino, P., Di Vito, M. A., Dolce, M., Iorio, A., Manunta, M., Monterroso, F., Pappalardo, L., Ricciolino, P., Roa, Y. L. B., Scarpato, G., Striano, P., and Lanari, R.: The 1 September 2025 geodetic event: a key phenomenon for understanding the unrest evolution at Campi Flegrei caldera (Italy), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14932, https://doi.org/10.5194/egusphere-egu26-14932, 2026.
Campi Flegrei, a restless caldera near Naples, Italy, has experienced significant ground uplift, elevated seismicity, and intense gas emissions over the past two decades. The physical source driving the observed deformation and seismicity remains debated, with proposed mechanisms including magmatic intrusion, hydrothermal pressurization, or hybrid processes. Recent seismic tomography images reveal a gas-rich reservoir at depths of ~2–3.5 km, coincident with concentrated seismicity, highlighting the potential dominant role of the shallow hydrothermal system.
In this study, we investigate whether a shallow reservoir can jointly explain both surface deformation and seismicity during the ongoing unrest. We use geodetic observations to constrain time-dependent volume changes of the shallow reservoir, integrating multi-year InSAR data from Sentinel-1 with continuous GPS measurements. To isolate signals associated with distinct deformation sources, we apply variational Bayesian Independent Component Analysis (vbICA). The reconstructed reservoir volume-change history is then incorporated into the induced-seismicity framework Flow2Quake to compute Coulomb stress changes, which are assumed to modulate seismic activity.
Our results show that volume changes within the shallow reservoir can consistently reproduce both the observed surface deformation and the spatial–temporal patterns of seismicity at Campi Flegrei. These findings place new constraints on the dominant source of unrest and improve our understanding of the coupled hydrothermal–mechanical processes governing the current state of the caldera.
How to cite: Cheng, J., Li, Z., Acosta, M., Lecampion, B., and Avouac, J.-P.: Source modelling of surface deformation and seismicity at the Campi Flegrei , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15110, https://doi.org/10.5194/egusphere-egu26-15110, 2026.
Understanding volcanic activity remains a challenging task. So far, several conceptual geodetic models have been proposed to describe the inter-eruptive period, typically invoking either progressive rock damage or increasing overpressure within the magmatic (or gas) reservoir. Here, we adopted a combined seismo-geodetic framework to investigate volcanic unrest and to model surface deformation at the Campi Flegrei (CF) volcano, Italy.
The CF caldera is one of the most active hydrothermal systems in the Mediterranean region and has experienced notable unrest episodes. Since 2005 a monotonic uplift phenomenon has been observed, accompanied by unsteadily accelerating seismicity (Bevilacqua et al., 2022).
Subsurface rocks sustain large strains and exhibit high shear and tensile strength (Vanorio & Kanitpanyacharoen, 2015). Consequently, seismicity reaches magnitude ~ 4.0 only upon relatively large uplifts ~70–80 cm during the 1980s unrest and >1 m during the recent episode), contrary to what is generally observed for calderas exhibiting much lower deformation levels (Hill et al., 2003).
The caprock above the seismogenic zone is characterized by a fibril-rich matrix that enhances ductility and resistance to fracturing (Vanorio & Kanitpanyacharoen, 2015). However, changes in pore pressure and/or chemical alteration may ultimately induce mechanical failure and modify the structural properties of subsurface rocks. In addition, increased magma pressure within the reservoir can weaken the volcanic edifice, leading to reductions in elastic moduli (Carrier et al., 2015; Olivier et al., 2019). In recent years, a quasi-elastic behavior and a stress memory effect of the upper crust of the CF caldera under increasing stress suggest a progressive mechanical weakening (Bevilacqua et al., 2024; Kilburn et al., 2017, 2023). Seismic tomography indicates that most of the observed seismicity is associated with a pressurized gas reservoir (De Landro et al., 2025), while advanced big-data-based earthquake locations exclude shallow magma migration (Tan et al., 2025). Furthermore, recent petrological and geochemical studies identified a weak layer that plays a key role in overpressure accumulation, driving both deformation and seismicity (Buono et al., 2025). The initiation and growth of a volcano-tectonic fault have also been hypothesized (Giordano et al., 2025).
In our study, we tracked the evolution of subsurface elastic properties by monitoring temporal changes in relative seismic wave velocities (δv/v) thanks to the coda wave interferometry of continuous ambient noise at local seismic stations. A progressive decrease in δv/v is detected in the area where we observe the highest concentration of seismicity and that we attribute to the rock-weakening tracked by the earthquake occurrences. By incorporating time-dependent elastic moduli changes in the geodetic inversion of surface displacement recorded by a local GPS network (De Martino et al, 2021), we retrieved a refined time evolution of reservoir overpressure. Our results suggest the active contribution of elastic properties of geomaterials in controlling the volcanic dynamics.
How to cite: Tarantino, S., Poli, P., Vassallo, M., D'Agostino, N., and Garambois, S.: Temporal elastic properties changes and rock weakening at Campi Flegrei, Italy, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11179, https://doi.org/10.5194/egusphere-egu26-11179, 2026.
Volcano deformation is an important precursor to eruptions, offering the opportunity to obtain information on the internal structure and magma plumbing system. Furthermore, deformation of volcanoes occurring after eruptions may also provide evidence of magma pathways and conduit dynamics, as demonstrated by this study. The 2021 Tajogaite eruption on La Palma was followed by progressive subsidence and the formation of major fracture networks surrounding the active craters. In this study, we analyse time-lapse data acquired using repeat drone photogrammetry and fixed-installation cameras to demonstrate that the aligned conduits withdraw and collapse over a time scale spanning from months to years following the eruption. Topography derivatives and pixel tracking show the convergence and subsidence of material into the possible conduit and the formation of inward-dipping normal faults affecting the inner and outer crater walls. To gain insights into the physical processes controlling the observations, we design models of conduit withdrawal that can reproduce the structures if topography and conduit burial are considered. Our findings suggest that the normal fractures surrounding the Tajogaite crater and numerous other craters are not the result of the eruption itself, but rather the consequence of volumetric reduction in the feeding conduit or dyke after the eruption.
How to cite: Walter, T. R., Ai, L., Zorn, E., and González, P. J.: Post-eruptive deformation and faulting caused by conduit withdrawal and subsidence of the 2021 Tajogaite craters (La Palma), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3537, https://doi.org/10.5194/egusphere-egu26-3537, 2026.
Between November 2023 – July 2025 there have been ten dike intrusions and nine fissure eruptions beneath Sundhnúkur, on the Reykjanes Peninsula, Iceland. Geodetic and geochemical analyses show that these have been fed by a common source, located at 3-4 km depth beneath the harnessed Svartsengi geothermal area. This remarkable sequence of magmatic activity has been marked by abundant seismicity. Relative quiescence on the Peninsula – following the July-August 2023 Fagradalsfjall eruption – was interrupted in late October by elevated seismicity and surface uplift measured at Svartsengi, 8 km further west. As during inflation episodes at Svartsengi in 2020 and 2022, intense shallow seismicity accompanied the deformation, dominantly consisting of strike-slip faulting above an inferred sill.
From around 15:00 on 10th November 2023, intense migrating seismicity and rapid metre-scale horizontal deformation marked the intrusion of a NNE-SSW oriented dike, which reached approximately 15 km length in just 8 hours, and propagated under the town of Grindavík, which was evacuated. On 18th December, similar (though smaller amplitude) signals marked a second, smaller intrusion, but in contrast this dike quickly breached the surface and culminated in a 4 km long fissure eruption. A similar pattern has repeated in the following 2 years, with cyclical re-inflation beneath Svartsengi, and repeated dike intrusions and fissure eruptions along a common lineament. Through analysis of high-resolution relative relocations of the dike-induced seismicity, we investigate the relative geometry of the repeated dike intrusions, and the relationship between the seismicity and distribution of dike opening and location of eruption onset.
We find that most dikes initiate from a common point, likely marking a repeatedly used connection to the shallow magma storage region beneath Svartsengi. The dikes vary in propagation direction, forming a complementary pattern of seismicity and inferred opening, and occupy at least two sub-parallel planes, which closely match the geometry of eruptive fissures at the surface.
How to cite: Winder, T., Heimisson, E. R., Gudnason, E. Á., Brandsdóttir, B., Rawlinson, N., Burjánek, J., Doubravová, J., Fischer, T., Hrubcová, P., Jónsdóttir, K., and Eibl, E. P. S.: Repeated dike injections beneath the Sundhnúkur crater row, Reykjanes Peninsula, Iceland, imaged by relatively relocated seismicity, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8103, https://doi.org/10.5194/egusphere-egu26-8103, 2026.
Understanding the transport of magma below the Earth’s surface is a key to studying volcanic systems. However, processes taking place at large depths are increasingly difficult to infer, since signals are often obscured by shallower processes. The Reykjanes Peninsula is an oblique rift zone in SW-Iceland and hosts several en-echelon arranged volcanic systems that experience contemporaneous rifting episodes over the course of 200-400 years. This episodic behaviour alternates with phases of volcanic quiescence lasting 800-1000 years. The occurrence of several eruptions since 2021 indicates the onset of a new phase of volcanic activity. Seismic and geodetic observations during recent years indicate that while at most one volcanic system appears to be active at any time on the peninsula, the focus of activity may shift abruptly between systems. Furthermore, while activity has focused on the Svartsengi volcanic system in 2023, the neighbouring Krýsuvík volcanic system has subsided at variable rates, indicating some degree of connection or communication between the systems.
We test this hypothesis of potential deep-seated communication by implementing lumped-parameter- and Finite Element models where the mid- to lower crustal magmatic plumbing systems within individual volcanic systems, connect to a zone underlying the peninsula near the crust-mantle boundary. This zone is thought to consist of discrete melt lenses, mush, partial melt and hot, ductile rock, and is rheologically weaker than its surroundings. The zone’s increased compliance relative to that of layers above and below allows for the transmission of pressure from one system to another. Pressure transfer does not require significant flow of material to occur between systems, allowing each volcanic system to keep its distinct geochemical characteristics.
In accordance with previous studies, the lumped parameter models represent the peninsula-scale magmatic system through several mid-crustal and one underlying, deep magma domain, all of which are connected through conduits and consist of melt lenses, mush and hot rock. The models reproduce several observed dynamics, including the temporary focus of activity on a single volcanic system, potential passive reactions in neighbouring systems, and abrupt transitions of activity between systems. Furthermore, the models underline the importance of considering processes and properties of the shallow plumbing system as well as volcano-tectonic interaction for deeper processes.
How to cite: Greiner, S. H. M., Geirsson, H., and Sigmundsson, F.: Models of deep interaction between volcanic systems during volcanic unrest and its implications for lower crustal structure and processes: Insights from the Reykjanes Peninsula, SW-Iceland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11866, https://doi.org/10.5194/egusphere-egu26-11866, 2026.
Volcano geodesy provides information about shallow magma domains (locations of magma) in volcanic areas, usually inferred through inversion of geodetic data giving a set of parameters, such as position and internal magma pressure change. These inversions require a model of the crust and the embedded magma domain, typically with an assumed specific shape for the magma domain. This shape is constrained to be parametrizable to be inverted for, thus is limited to classical regular shapes among spheres, ellipsoids and sills, which are unlikely to capture the morphological complexity of actual magma domains. Here, we present an alternate approach to invert for the shape of the magma domain without requiring any prior assumptions about it, based on recent techniques from the field of shape optimization. Instead of optimizing a finite vector of parameters, the entire shape of the magma domain is optimized to minimize the discrepancy between observed ground displacements and those predicted by the model, under the assumption of an elastic crust. More precisely, our strategy relies on a “shape gradient'' descent based on the concept of shape derivative and on the level set method to track changes in the magma domain boundary. We provide magmaOpt, a Python and FreeFEM based code that iteratively performs the shape gradient search and solves successive partial differential equations that govern the problem on an evolving mesh of the area of interest. First, we demonstrate the potential of the method using a test case with synthetic data. Then, we apply the method to data from interferometric analysis of synthetic aperture radar satellite images (InSAR) observations of the 2022 inflation episode in Svartsengi, Iceland, to explore possible shapes of the magma domain responsible for the inflation. This work paves the way for a new class of methods that provide more information on magma domains and ultimately lead to better volcanic hazard monitoring.
How to cite: Perrot, T., Sigmundsson, F., and Dapogny, C.: Reconstructing the Shape of Magma Domains from Observations of Ground Deformation in Volcanic Regions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2812, https://doi.org/10.5194/egusphere-egu26-2812, 2026.
The coupling between surface topography and subsurface magma dynamics in volcanic rift zones is a well-established concept; however, quantitative constraints on this interaction remain rare and not systematically explored. In this study, we integrate high-resolution geodetic data from satellite and drone-derived digital elevation models to study eruption vents, cones and associated fractures from the two largest fissure eruptions in historical time, i.e., the Laki (1783–1784) and Eldgja (939–940) eruptions, each tens of km long and hosting dozens of eruptive vents. Comparing cone morphometrics with analytical stress models reveals a statistically significant inverse correlation between topography-induced compressive stress and cone volume. We show that increased confining stress at higher elevations narrows feeder dykes, reducing eruptive efficiency and producing smaller cones. Conversely, larger cones dominate in topographic lows where loading is minimized. Furthermore, we find that steep slopes generate high stress gradients that drive fissure segmentation, arresting lateral propagation and trapping magma beneath mountains. Our models also help to explain why variations in topography correlate with a transition from symmetric grabens in flat terrain to asymmetric fault offsets in complex terrain due to topography-driven vertical shear stress. These findings move beyond conceptual models and establish topography as a predictive parameter for along-rift vent location, discharge patterns, and surface deformation, offering a quantitative framework for volcanic hazard assessment in rift zones.
How to cite: Hurley, M., Maccaferri, F., and Walter, T. R.: Topographic controls on fissure eruptions at Lakagigar and Eldgja, Iceland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5406, https://doi.org/10.5194/egusphere-egu26-5406, 2026.
Dike propagation governs how magma is transported and emplaced within the crust, fundamentally controlling eruption dynamics and the mechanical state of volcanic systems. Understanding its evolution is therefore essential for assessing volcanic hazards and crustal stress redistribution. Seismicity, which occurs as a dike fractures and deforms the surrounding host rock, provides key evidence for tracking the geometry, velocity, and temporal evolution of dike propagation. While the forward (tipward) propagation of dikes, accompanied by migrating seismicity, has been extensively studied, episodes of backward seismic migration—where earthquakes progress opposite to the main propagation direction—remain poorly understood. The physical mechanism responsible for this phenomenon and its relationship to magma pressure evolution and host-rock damage are still uncertain. To address this, we developed a damage-mechanics-based finite element model that couples fluid dynamics and solid mechanics to simulate the interactions between magma pressure, fracture propagation, and inelastic deformation of the surrounding rock. The model reproduces both forward and backward seismic migration patterns by incorporating stress redistribution and fracture reactivation following transient pressure drops during dike propagation. We apply this framework to the 2014–2015 Bárðarbunga diking events in Iceland—one of the most comprehensively monitored lateral intrusions—to identify the controlling processes behind the observed backward propagation of seismicity. Model results suggest that back-propagation arises from the reactivation of previously damaged segments as magma pressure decays and stress is transferred back along the dike. Our findings provide a mechanistic explanation for the dual propagation behavior of seismicity during dike intrusions and establish a physically grounded approach for linking seismic migration to magma dynamics and crustal damage evolution in active volcanic systems.
How to cite: Zhan, Y., Huang, Y., and Chan, Y. Y.: Backward Propagation of Seismicity During the 2014–2015 Bárðarbunga Diking Events, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8453, https://doi.org/10.5194/egusphere-egu26-8453, 2026.
Askja volcano's ongoing inflation since August 2021 (+85 cm uplift) presents a unique opportunity to study coupled magmatic-hydrothermal processes during sustained volcanic unrest. Concurrent observations of seismic velocity decrease (dv/v) at ~2 km depth and decreasing surface thermal anomalies (>1 K) suggest that hydrothermal circulation actively responds to magmatic intrusions. In this project, we aim to understand how hydrothermal processes modulate surface deformation and thermal emissions during magmatic injections at depth using coupled thermo-poroelastic, Finite Element Method (FEM), numerical models. Our models (built with COMSOL Multiphysics) integrate solid mechanics, Darcy flow, and heat transfer in porous media, representing a permeable hydrothermal reservoir above a sill intrusion at 2.6 km depth. Sill geometry is constrained by elastic inversions of geodetic data from Parks et al. (2024). Permeability depends on effective stress (exponential reduction under compression), temperature (exponential increase with heating), and volumetric strain (cubic modification of porosity).
Long-term simulations provide initial conditions with background thermal and hydraulic gradients, followed by a 4-year perturbation simulating the magma intrusion through increased heat flux and a prescribed displacement rate (0.21 m/year). Results show that compression at depth creates a low-permeability seal, trapping heat and pressurized fluids below. Beneath the seal, temperature increases, consistent with observed dv/v decreases at 2 km depth; while above the seal, reduced fluid circulation causes surface cooling of less than 1 K, explaining the decrease in thermal anomalies detected in satellite observations.
Our preliminary results suggest that multi-parameter observations at Askja (geodetic, seismic velocity, thermal anomalies) can be explained through coupled thermo-poroelastic processes, showing that hydrothermal system dynamics should be considered to interpret monitoring data during volcanic unrest.
How to cite: Brenot, L., Girona, T., Le Mével, H., Gossez, M., Peiffer, L., García-Martínez, N., Jónsdóttir, K., and Caudron, C.: Coupled magmatic-hydrothermal processes during ongoing inflation at Askja volcano, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10577, https://doi.org/10.5194/egusphere-egu26-10577, 2026.
To understand how magma propagates in the crust, displacement data are analyzed using models combined with inversions. Most often, the fracture geometry is assumed and discretized into dislocations, whose amplitude is determined by linear inversions. However, determination of dislocations is not as physical and parsimonious as determination of stress changes. In addition, most dislocation solutions assume that the Earth is an elastic and homogeneous half-space, which can lead to inaccurate results, as volcanoes are intrinsically heterogeneous (Montgomery-Brown et al., 2009; Masterlark, 2007).
To resolve pressure instead of dislocations, a method (Smittarello et al., 2019a and 2019b) was previously implemented that relied on the combination of InSAR and GNSS data, where InSAR data covering an eruption were used to determine the geometry of the eruptive fracture and GNSS data were used to track the pressurized part of this fracture. This method was applied to the May 2016 Piton de la Fournaise (Réunion Island, France) eruption, showing that magma first intruded in a sill before turning into the dike that fed the eruption.
In order to take medium heterogeneities into account, we propose a new method (Dabaghi et al., 2026) based on a fictitious domains approach (Bodart et al., 2016). As we use finite elements, heterogeneous media can be taken into account. The cost function involves a misfit, as well as regularization terms. An algorithm is presented based on the direct problem and the adjoint problem. Synthetic tests demonstrate that the method is efficient and robust for one to four InSAR observations in different lines of sight, even in the presence of missing data and noise. The method also works for GNSS data. Finally, our method was tested on the May 2016 eruption of Piton de la Fournaise, showing results consistent with our previous analysis, providing further validation.
How to cite: Cayol, V., Dabaghi, F., Bodart, O., Smittarello, D., and Pinel, V.: Resolving traction changes on fractures in volcanic or tectonic contexts, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5506, https://doi.org/10.5194/egusphere-egu26-5506, 2026.
Detecting lava tubes is challenging in the field due to their hidden nature and inaccessibility, but it can be important for understanding lava flow dynamics and mitigating hazards. Here we show how analysis of multispectral imagery (Sentinel-2 and Landsat) and InSAR (Sentinel-1) can enable the delineation of a ∼14-km long lava-tube network entirely by remote sensing. The lava tube network formed in 2024 during the 68-day long eruption of Fernandina volcano, a highly active, yet remote and uninhabited island in the Galapagos Islands. The arterial tube(s) and main branches of the network were mapped based on: (1) spatio-temporally stable, point-like thermal anomalies (“skylights”) from syn-eruption shortwave and thermal infrared imagery; and (2) a dendritic pattern of horizontal displacements defined by post-eruption InSAR timeseries analysis. Furthermore, elongated perpendicular baselines of Sentinel-1 interferograms enabled us to estimate lava-flow thicknesses of up to ∼17 m locally and a lava-field bulk volume of ∼84 ± 40 × 106 m3. Lastly, we traced the growth of the lava field from a time series of InSAR coherence images. Combined with the lava thickness mapping, the coherence mapping gives initial magma eruption rates of 87 m3s−1, which over two weeks declined rapidly and non-linearly to below 6 m3s−1. This sharp reduction in eruption rate coincides with a transition - observed in multispectral imagery - from initial open channel flow to enclosed tube flow. Although the tube flow phase accounted for only 18% of the total erupted volume, it spanned 75% of the eruption duration and facilitated 35% (5 km) of the total lava run-out. These entirely remotely generated results are consistent with field‐based observations of lava tube development on Hawaii. A multi-sensor approach to remote sensing of lava tubes may therefore contribute in future to modelling of lava flow advance and to assessment of tube-collapse hazard.
How to cite: Holohan, E., Hrysiewicz, A., LaFemina, P., Bell, A., Galetto, F., Vallejo, S., and Bernard, B.: The geometry and development of a lava tube network as deduced from multispectral imaging and InSAR, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20302, https://doi.org/10.5194/egusphere-egu26-20302, 2026.
Posters on site: Tue, 5 May, 16:15–18:00 | Hall X2
Sakurajima volcano, located on the rim of the Aira caldera in Japan, represents a major hazard for the heavily populated area of Kagoshima Bay. In recent decades, ground deformation modelling and seismic imaging have inferred the presence of a large magma reservoir ~10-15 km below Aira caldera [1] and one or multiple shallower reservoirs below Sakurajima [2, 3]. Understanding the connectivity between these reservoirs is critical for hazard assessment, as deep-melt migration into the shallow system can trigger major eruptions [4]. To this end, accurate models of the magma plumbing system are needed, considering both realistic reservoir geometries and the possibility of magma storage in dynamic magma-mush systems rather than melt-filled cavities. Modelling reservoir stability and magma transport also requires realistic estimates of the state of stress underground. In this regard, the location of Aira caldera within the Kagoshima graben offers a unique case study, as the regional stress field is likely modulated by various factors beyond reservoir pressurisation. In this study, we employ Finite-Element numerical modelling [5] and recent GNSS and seismic tomography data to investigate the coupled plumbing systems of the Aira-Sakurajima complex, describing the deep reservoir as a poroelastic magma mush. First, we use ground deformation data to constrain the geometry and location of the reservoirs, as well as melt supply parameters. We introduce a complex geometry for the deep reservoir inferred from seismic tomography [1], assessing its influence on deformation modelling compared to previously employed simplified geometries. We also estimate the volume of the active magma source, providing an upper limit to the magnitude of current eruptions. Finally, we integrate the best-fit model of plumbing system architecture and pressurisation into stress models including gravitational loading and tectonic stress to identify the conditions for magma exchange between the deep and shallow reservoirs, which might escalate volcanic risk at Sakurajima.
References:
[1] Tameguri et al. (2022) Bulletine Volcanological Society Japan, https://doi.org/10.18940/kazan.67.1.69
[2] Araya et al. (2019). Scientific Reports, https://doi.org/10.1038/s41598-019-38494-x
[3] Hotta et al. (2016). Journal of Volcanology and Geothermal Research. http://dx.doi.org/10.1016/j.jvolgeores.2015.11.017
[4] Hickey et al. (2016). Scientific Reports, https://doi.org/10.1038/srep32691
[5] Mantiloni et al. (2026). Journal of Geophysical Research: Solid Earth, under review.
How to cite: Mantiloni, L., Hickey, J., Alshembari, R., McCormick Kilbride, B., Tsutsui, T., Daisuke, M., Tameguri, T., and Nakamichi, H.: Modelling magma storage and transport in Aira Caldera and Sakurajima Volcano, Japan., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11203, https://doi.org/10.5194/egusphere-egu26-11203, 2026.
Seismic activity in volcanic regions is strongly influenced by spatio- temporal changes in stress and crustal strength associated with magma intrusion and fluid migration. We investigate to capture these processes using the seismic moment ratio, Mstk/M0, defined as the ratio of the norm of a stacked seismic moment tensor to the sum of scalar seismic moments of individual earthquakes. This parameter provides a quantitative measure of crustal criticality, approaching unity for optimally oriented slip under high stress and decreasing under reduced strength or heterogeneous stress conditions.
We apply this approach to the Kirishima volcanic area, Kyushu, Japan, where volcanic activity has repeatedly intensified and declined over the past two decades. Focal mechanism solutions derived from waveform data recorded by permanent and temporary seismic networks between 2000 and early 2025 were analyzed. Seismic moment tensors were estimated from focal mechanisms and magnitudes and stacked within spatial blocks containing at least 20 events.
The inferred stress field indicates a strike-slip to normal-faulting regime around Shinmoe-dake, with the minimum principal stress axis oriented northwest–southeast, consistent with regional vent alignment. Spatially, Mstk/M0 values are systematically lower near Shinmoe-dake than in surrounding regions, suggesting locally reduced crustal strength and/or short-wavelength stress heterogeneity. Temporally, Mstk/M0 exhibits large fluctuations near the volcanic center, whereas values remain consistently high in distal areas. Comparison with focal mechanism misfit angles indicates that these variations are primarily controlled by temporal changes in medium strength, likely driven by magmatic fluids. Our results demonstrate that Mstk/M0 is a useful proxy for monitoring evolving stress–strength conditions in active volcanic systems.
How to cite: Matsumoto, S., Hirata, I., Nagayama, Y., Emoto, K., Matsushima, T., Ichihara, M., Yukutake, Y., and Yakiwara, H.: Tracking volcanic stress and strength changes using the seismic moment ratio (Mstk/M0) at Kirishima volcano, Kyushu, Japan, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3835, https://doi.org/10.5194/egusphere-egu26-3835, 2026.
Fluids play a pivotal role in altering rock mechanics by affecting shear strength and influencing strain accommodation. This study integrates GNSS time-series and seismological data to reconstruct the spatiotemporal evolution of deformation during 2021 within the Peloritani Mountains (NE Sicily) and the Aeolian Archipelago. Our analysis identifies significant crustal-scale deformation along the NNW-SSE right-lateral transtensional Aeolian-Tindari-Letojanni Fault System (ATLFS), as well as in WNW-ESE to NW-SE right-lateral transfer zones in the western and central sectors of the Aeolian Archipelago. Specifically, throughout 2021, we observed a distinct acceleration in deformation rates along the eastern block of the ATLFS relative to its western counterpart. This kinematic anomaly was strictly synchronous with a peak in seismic strain release and a significant unrest phase at Vulcano Island, characterized by rapid ground inflation and intense degassing. The temporal correlation between tectonic slip and volcanic activity suggests that enhanced fluid circulation—evidenced by gas emissions in the Peloritani area— may modulate the mechanical response of faults, promoting strain release. These findings provide critical constraints on the interplay between active tectonics, fluid migration, and volcanic processes in the Central Mediterranean.
How to cite: Mattia, M., Messina, D., Corradino, M., Barberi, G., Bruno, V., Patanè, D., Rossi, M., Scarfì, L., and Pepe, F.: Fluid-Driven Fault Mechanics and Strain Release: Insights from the 2021 Deformation Episode in the Peloritani-Aeolian Sector, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20322, https://doi.org/10.5194/egusphere-egu26-20322, 2026.
Fluids play a fundamental role in controlling deformation, stress redistribution, and seismicity in volcanic and geothermal systems. Variations in pore pressure and temperature associated with hydrothermal circulation can significantly alter the mechanical state of the crust, particularly during unrest episodes in volcanic scenario. Classical analytical models, such as the Mogi point source, have been widely used to interpret surface deformation induced by magmatic intrusions. However, these formulations neglect thermo-poro-elastic coupling and predict an isotropic stress state within the source, thus failing to account for seismicity occurring inside the deformation source.
Thermo-poro-elastic (TPE) theory provides a physically consistent framework to describe the coupled effects of fluid pressurization and heating in porous media. Analytical thermo-poro-elastic inclusion models have recently demonstrated their effectiveness in reproducing stress heterogeneities and associated focal mechanisms both internal and external to the source.The inclusion represents a finite, permeable region affected by temperature and pore-pressure variations, while the surrounding medium is assumed to be in isothermal and drained conditions. Nonetheless, at present time, the available solutions for spherical inclusions are derived for an infinite medium, limiting their applicability when surface observations are considered, especially for shallow sources.
In this study, we develop new fully analytical solutions for spherical and spherical shell TPE inclusions embedded in a half-space, explicitly accounting for the presence of a free surface. Closed-form expressions are obtained for displacement, strain, and stress fields throughout the domain, including within the source.
The problem is formulated under an axisymmetric hypothesis using cylindrical coordinates. Free-surface boundary conditions are enforced through a combination of the image source method and the Galerkin approach. The methodology is first applied to a spherical TPE inclusion representing a pressurized and heated reservoir, and subsequently extended to a spherical magmatic source surrounded by a spherical TPE shell, modeling a mechanically distinct fractured zone surrounding a magma chamber.
The results show that the free surface strongly modifies deformation and stress fields compared to full-space solutions. For shallow sources significant differences arise in all mechanical fields. In the spherical shell configuration, thinner shells exhibit enhanced internal shear stress and reduced external deformation, suggesting a higher susceptibility to internal failure.
The model is applied to the 2021 unrest episode at Vulcano Island. Using source parameters constrained by previously published we found that significant shear stress concentrations are predicted within and around the source, providing a physically consistent explanation for the clustered shallow seismicity observed near the crater. These results highlight the importance of TPE coupling and free-surface effects in the interpretation of volcanic unrest processes and fluid-driven seismicity.
How to cite: Battolini, S., Nespoli, M., and Belardinelli, M. E.: Deformation of shallow thermo-poro-elastic spherical sources and the 2021 Vulcano Island (IT) unrest, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9973, https://doi.org/10.5194/egusphere-egu26-9973, 2026.
Strain data recorded by Sacks-Evertson strainmeters, due to the high dynamic of the instrument and since its output responds to input over a wide frequency range, are prone to be affected by anthropic noise, changes in atmospheric pressure, tides, rainfall, underground water movements, changes in underground temperature, earthquakes, as well as other crustal movements. Several kinds of procedures have been developed over time by geophysicists to remove the unwanted (“spurious”) signals from the actual recordings, in order to thereby obtain cleaner strain data, capable of representing the actual changes of the local strain in proximity to the installation site. The clearly most dominant signals in a strain data time series are associated with Earth tides and atmospheric pressure loading. Earth tides, due to the relative motion of Sun and Moon with respect to Earth, account for 10−10 strain over a frequency range of 10−4–10−5Hz (periods of hours to days), and are induced by periodic, measurable forces: this allows a reproducibility of the phenomenon using numerical simulations software. On the other hand, atmospheric pressure, for its own characteristics, is a highly variable signal, spanning over extremely wide strain- and frequency-ranges. Both signals, however, are characterized by frequencies comparable with those of interest. One of the most successful methods to remove tides and atmospheric pressure uses a combination of harmonic and non-harmonic techniques, through the implementation of Bayesian statistics. The software assumes that a given signal can be decomposed into a tidal component, a trend term, a perturbation due to an external source, the atmospheric pressure, responsible for generating a change in the recorded signal, and some random noise superimposed.
Barometric admittance quantifies how rock/soil strains to atmospheric pressure changes, often modeled linearly but non-linearities arise from complex subsurface media (aquifers, faults, cracks), requiring advanced techniques like neural networks or state-space models to capture frequency-dependent responses, revealing aquifer properties, fault activity, or seismic precursors, with higher frequencies showing local effects and lower frequencies reflecting regional pathways, indicating that strain varies nonlinearly with pressure due to medium heterogeneities.
The data recorded by a Sacks-Evertson strainmeter installed at Stromboli volcano show a non-linear relationship between barometric pressure and strain variations for lower frequencies: an empirical mode decomposition has been used considering the frequency dependent characteristics of the pressure response and the borehole strain observation data, and the pressure observation curve of synchronous observation are decomposed, obtaining the frequency dependent pressure response coefficient, realizing the refined pressure correction of borehole observation data.
In the higher frequency range, when the medium shows an elastic response related to pressure changes, a linear regression model in the time domain has been carried out to highlight volcanic-related strain changes.
This analysis could improve the volcanic hazard assessment of strain data related to open-conduit volcanoes, such as Stromboli, during unrest phases.
Data used contains valuable information for scientific community and are made available on the EPOS data portal. Attention is taken into metadata handling and intelligent management of distributed resources.
How to cite: Romano, P., Di Lieto, B., Mangiacapra, A., Petrillo, Z., and Sangianantoni, A.: Analysis of relationship between strain and atmospheric pressure data at Stromboli volcano, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19509, https://doi.org/10.5194/egusphere-egu26-19509, 2026.
Campi Flegrei caldera has experienced a critical increase in uplift rates over the past 20 years. Recent geodetic and seismic data indicate significant ground deformation (~18 cm in 2024) as well as increasing seismicity rates and magnitudes, further prompting the ongoing debate about the underlying causes. While shallow magma transport is often invoked to explain the deformation, other studies point to the accumulation of fluids in the shallow crust as primary drivers of overpressure and surface displacement. Disentangling the contribution of these processes remains a key challenge. In this study, we aim to quantify the uplift resulting from potential shallow magma migration and determine whether the deformation can be attributed mainly to it.
To address this, we integrate constraints from seismic imaging, geodesy, and rock physics into a 3D thermo-mechanical model with a visco-elasto-plastic rheology. Employing the available structural information on the caldera, the model features a deep magma influx originating from a depth of 8 km, feeding a shallower reservoir at approximately 5 km depth. We test the potential contribution of upward magma migration to surface deformation. We further explore how a mechanically weak shallow tuff layer and the hydrothermal system influence the response to the magmatic intrusion. The results show whether shallow magma migration should be paired with the effects of overlying structures and rheologies. The thermo-mechanical model reproduces only part of the observed surface deformation implying additional pressure sources, such as volatile exsolution or hydrothermal pressurization - which are not explicitly modeled here - play a significant role.
Thermo-mechanical modeling thus discriminates the role of magma in the ongoing deformation and provides insights into how stress builds and evolves in the system due to magma migration. These results are crucial for improving our comprehension of the deformation sources at Campi Flegrei and their interactions with shallow structures for seismic modeling purposes.
How to cite: De Siena, L., Nardoni, C., and Spang, A.: Quantifying the contribution of magma intrusion to the current unrest at Campi Flegrei caldera through thermomechanical modeling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5225, https://doi.org/10.5194/egusphere-egu26-5225, 2026.
The 1538 Monte Nuovo event — the most recent eruption at Campi Flegrei —represents a key benchmark for understanding volcanic unrest at the caldera. Its preparatory phase exhibits significant parallels with modern non-eruptive unrest episodes (1950–1952, 1969–1972, 1982–1984) and the ongoing crisis (2005–present). While historical accounts, archaeological records, and field observations have previously allowed for detailed reconstructions of the pre-eruptive activity, these have largely provided static quantitative snapshots of pre-eruptive phases. This study translates these reconstructions into a physics-based modeling framework for Monte Nuovo pre-eruptive dynamics. We simulate the magma transport process during the two-year lead-up to the eruption, focusing on the propagation of a magmatic intrusion from a central shallow sill (~3 km depth) to the peripheral Monte Nuovo vent (~4 km away from the sill center). Our results test the robustness and consistency of previous findings, and isolate the effect of magma dynamics to the ground deformation, providing new insights on the magnitude of the magmatic vs hydrothermal contributions to uplift signals. This work offers critical implications for interpreting modern monitoring data and evaluating possible scenarios of unrest evolution should a Monte Nuovo-like event become increasingly probable.
How to cite: Maccaferri, F., Trasatti, E., Rivalta, E., Passarelli, L., and Pappalardo, L.: Dyke propagation scenarios feeding the Monte Nuovo eruption (1538 CE) at Campi Flegrei caldera (Italy): insights into magma dynamics and implications for unrest., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10745, https://doi.org/10.5194/egusphere-egu26-10745, 2026.
Vesuvius is one of the volcanoes with the highest volcanic risk worldwide, owing to the exceptionally dense urbanization of its surroundings. Its eruptive history is well constrained from 1631 to the present, while the period preceding this date, particularly the 15th and 16th centuries, remains poorly defined. During this interval, the volcano is generally believed to have undergone a prolonged phase of quiescence, although several historical reports describe episodes of activity. This time window is of critical importance for the correct interpretation of Vesuvius’s eruptive behavior, especially in understanding the relationship between large, explosive eruptions, such as the 1631 event, which represents the reference scenario in the current national emergency plan, and the more frequent effusive or mixed eruptions that characterized the volcano’s persistent activity pattern.
Previous studies have undertaken a critical re-examination of the historical “accounts” of volcanic activity during the 16th century in light of new scientific, historical, and art-historical evidence. These analyses have revealed previously unrecognized features of Vesuvius’s behavior prior to the major eruption of 1631, identifying elements that merit further investigation. Moreover, further research is needed to clarify the relationships between Vesuvius and the nearby Campi Flegrei caldera. Historical records indicate that, during the 16th century, the activity of the two volcanic systems was concurrent, suggesting possible interactions or mutual modulation of their behavior. In addition, Rosi et al. (2025) show that the long-term unrest that preceded the Monte Nuovo eruption (1538), which affected the Campi Flegrei area during the 15th and 16th centuries, represents the only historically documented unrest episode prior to the one currently underway. This aspect is of fundamental importance for interpreting the present unrest at Campi Flegrei, which has been ongoing for more than twenty years and continues to show progressive intensification and spatial expansion.
How to cite: Giudicepietro, F., Calabria, P., Cubellis, E., Giacomelli, L., Macedonio, G., Martini, C., Pappalardo, L., Pirovano, D., Priolo, C. G., Scandone, R., and Leone de Castris, P.: Insights into the possible relationships between the Vesuvius and Campi Flegrei volcanic systems in the sixteenth–seventeenth centuries through artistic and literary sources, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12492, https://doi.org/10.5194/egusphere-egu26-12492, 2026.
Direct observations of dike intrusions during continental magmatic rifting are rare. Therefore, magma plumbing systems and associated hazards in continental rifts are not well understood. The 2024-2025 rifting event in the Fentale-Dofen magmatic segment of the Main Ethiopian Rift involved the prolonged intrusion of a ~50 km long dike into ~35 km thick continental crust lasting over 3 months, accompanied by deflation of a ~6 km deep magma reservoir beneath Fentale. Satellite-based Interferometric Synthetic Aperture Radar (InSAR) observations at regular intervals throughout the intrusion allow us to monitor the co-evolution of the magma source and the intrusion using surface deformation data, in the absence of ground-based instrumentation.
Modelled dike volumes (>1 km3) are 4-9 times larger than the volume loss of the deflating magma reservoir beneath Fentale. At other systems, this volume mismatch has been attributed to host rock rigidity, reservoir geometry, and magma compressibility. While the total dike to source volume ratio is typically reported, this ratio can vary during the diking event due to changes in gas content and compressibility, or involvement of multiple sources. Temporally-dense displacement measurements of the intrusion at Fentale present an opportunity to investigate the evolution of the dike to source volume ratio during a continental rifting event, providing a novel constraint on the conditions for magmatic storage and transport.
We propose that tracking the geodetic volume balance between the dike intrusion sink and reservoir source over time could be used as a tool to reveal changes to the magmatic system, in the absence of other observations (i.e., seismological or petrological). We present a timeseries of intrusion to source volume ratio, derived from analytic kinematic models of surface displacements. We use the relative volumes as a proxy to infer whether and how the mechanical properties of the magma, or the magma source(s) being tapped by the dike changed over time. We show that the volume balance timeseries suggests a change in the magmatic system during the intrusion, possibly related to deeper changes in the plumbing system that caused emissions of methane and carbon dioxide in January 2025 and a ~19 km deep non-double-couple earthquake in February 2025.
Pre-diking inflation and post-diking ground uplift around Fentale points towards magmatic recharge and re-pressurisation of a reservoir that is distinct from the co-diking shallower deflating source. The interpretation of a single magma source feeding a lateral dike intrusion may be insufficient to explain the geodetic observations of the intrusion, where the spatial and temporal connectivity of magmatic reservoirs is not trivial. Continuous monitoring of deformation will contribute to our understanding of threshold conditions for reservoir failure, with implications for forecasting the spatio-temporal likelihood of future intrusions.
How to cite: Way, L., Biggs, J., Wimpenny, S., Zheng, W., Orrego, S., Davis, T., W. Dualeh, E., Lazecky, M., Wright, T., and Lewi, E.: Reservoir connectivity in a continental rift: Insights from geodetic observations during the 2024-2025 dike intrusions at Fentale, Main Ethiopian Rift, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12106, https://doi.org/10.5194/egusphere-egu26-12106, 2026.
Dike intrusions commonly generate normal faulting and graben structures in volcanic rift zones, but distinguishing magma-driven deformation from regional tectonics remains challenging, especially where pre-existing faults, topography, and lithological contrasts coexist. Here we document a previously unrecognised mechanism of magmatically driven antithetic faulting, based on an integrated field and numerical study from the Fremrinámur Rift, Northern Iceland.
We investigate a N–S-trending graben developed entirely on a Late Glacial subglacial pillow lava–hyaloclastite cone, without deformation of the surrounding lava plateau. High-resolution UAV photogrammetry combined with detailed field mapping reveals a strongly asymmetric graben geometry: the eastern fault, aligned with the rift-border fault, displays vertical offsets up to one order of magnitude larger than the western fault. Eruptive fissures at the northern and southern base of the cone suggest a single dike intrusion event that failed to propagate to the cone summit.
To explore the controlling mechanisms, we performed 2D finite-element numerical models simulating dike-induced stress and surface deformation under varying dike dip, intrusion depth, interaction with a pre-existing fault, and host-rock rheology. The models show that an inclined dike propagating along a pre-existing rift-border fault, combined with a strong mechanical contrast between the competent basaltic substratum and the weaker subglacial cone, produces pronounced stress and displacement asymmetry. In this configuration, von Mises shear stresses concentrate within the hanging-wall block, promoting the formation of an antithetic fault, while tensile stresses above the dike tip are significantly reduced, favouring dike arrest within the cone.
These results highlight the combined role of fault inheritance, topography, and lithological heterogeneity in controlling dike-induced deformation, fault asymmetry, and intrusion arrest in volcanic rift environments.
How to cite: Bonali, F. L., Brando, S., Pasquaré Mariotto, F., Luppino, A., and Tibaldi, A.: Magmatically driven antithetic faulting on a topographic high: field and numerical insights from Northern Iceland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12475, https://doi.org/10.5194/egusphere-egu26-12475, 2026.
Askja, an active basaltic caldera volcano in Iceland’s Northern Volcanic Rift Zone, has experienced more than 85 centimetres of surface uplift since August 2021, following several decades of subsidence. Geodetic modelling of the observed uplift suggests an inflating sill type source at around 3 km below the surface (Parks et al., 2024), and recent tomography work by Han et al (2024) and Fone et al. (2025) image a shallow low-velocity anomaly, centred on the area of maximum uplift. In the same month that uplift began, there was a clear increase in the rate of shallow microseismicity, observed primarily in clusters surrounding the youngest lake-filled caldera Öskjuvatn.
To gain more insight into how the change in rate of microseismicity relates to the observed reversal in surface deformation, moment tensor solutions were constructed for a subset of events beneath Askja, both before and after the start of re-inflation. The Cambridge Volcano Seismology Group has maintained a dense seismic network around Askja since July 2007, which provides sufficient azimuthal coverage to produce well constrained moment tensor solutions. An expanded network deployed within Askja caldera in summer 2023 improves this azimuthal coverage significantly, extending the smallest well constrained events from magnitude 0.5 to just below magnitude 0.
Our results provide new constraints on the ring fault geometry beneath Öskjuvatn – where the microseismicity rate increase was most prominent – complementing previous insights from mapping of surface faults. Surprisingly, there is no evidence for a reversal in earthquake slip direction associated with the start of re-inflation, and only the modelled stress changes during the re-inflation period favour slip that aligns with our moment tensor solutions. We therefore propose that the microseismicity prior to the onset of re-inflation may have been driven primarily by regional deformation processes, not the long-term subsidence within Askja caldera. Our future work will exploit this expanded dataset of manually picked earthquake phase arrivals to improve our resolution of the velocity structure at the shallowest depths beneath Askja. This will contribute to a full structural model linking surface deformation, ring faulting and the underlying magma storage region.
Citations:
Han, J., N. Rawlinson, T. Greenfield, R. White, B. Brandsdóttir, T. Winder, and V. Drouin (2024),
Evidence of a shallow magma reservoir beneath askja caldera, iceland, from body wave tomography, Geophysical Research Letters, 51 (9), e2023GL107,851
Parks, M. M., F. Sigmundsson, V. Drouin, S. Hreinsdóttir, A. Hooper, Y. Yang, B. G. Ófeigsson, E.
Sturkell, Á. R. Hjartardóttir, R. Grapenthin, et al. (2024), 2021–2023 unrest and geodetic
observations at askja volcano, iceland, Geophysical Research Letters, 51 (4),
e2023GL106,730.
Fone, J., Winder, T., Rawlinson, N., White, R., Brandsdóttir, B., and Soosalu, H. (2025), Imaging the
shallow structure beneath Askja volcano, Iceland, with ambient noise tomography, Journal of Geophysical Research: Solid Earth, 130 (12), e2025JB031,905.
How to cite: Siggers, I., Winder, T., Rawlinson, N., White, R. S., and Brandsdóttir, B.: Earthquake focal mechanisms reveal a complex response to re-inflation at Askja caldera, Iceland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17905, https://doi.org/10.5194/egusphere-egu26-17905, 2026.
Askja is one of the most monitored volcanoes in Iceland. Since 1966, annual ground deformation measurements have been carried out in Askja along a leveling line. In 1993 the first Global Navigation Satellite System (GNSS) measurements were made in Askja and in 1992 the first Interferometric Synthetic Aperture Radar (InSAR) images of Askja were gathered. Since 2021 there has been uplift at Askja volcano, after decades of subsidence. The uplift is monitored with GNSS and InSAR measurements. The net uplift from June 2021 to December 2025 is approximately 90 cm with a decreasing rate. Previous geodetic models of the observed ground deformation inferred an inflation source at a median depth of 2.7 – 2.8 km. Gravity surveys have been carried out regularly since 1988, and annually since 2018. Gravity measurements show mass or density changes in the sub-surface. From 1988 – 2017 there was a net gravity decrease, while measurements from 2017 – 2023 show a net gravity increase during that period.
We carried out GNSS campaigns and gravity surveys in August of 2024 and 2025. We measured 18 gravity stations and 20 GNSS stations scattered around Askja. The gravity was measured with two relative spring gravimeters (Scrintex CG5 and CG6). Gravimeters are very sensitive and prone to sudden data tares, to mitigate this we used two meters. We can evaluate the uplift between years with GNSS and InSAR data and apply the theoretical Free Air gradient to correct for the gravity change due to elevation change. The yearly uplift rate 2023 - 2025 is up to about 10 cm/year. After correcting for the height changes, preliminary evaluation suggests that the net gravity change from 2023-2025 does vary between stations, with increase at some stations and decrease at others. By analyzing the gravity change we are adding another parameter to our dataset, which helps us to identify the process responsible for the current uplift episode.
How to cite: Sigurðardóttir, F. M., Sigmundsson, F., van Dalfsen, E., Drouin, V., Parks, M. M., Geirsson, H., Yang, Y., and Ófeigsson, B. G.: Change in microgravity during an inflation episode at Askja Volcano, Iceland, 2023 – 2025, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17192, https://doi.org/10.5194/egusphere-egu26-17192, 2026.
The most recent eruption of Fernandina volcano in the Galapagos Islands took place in March 2024. Subsequently, during the latter part of 2024 and the first half of 2025, the volcano showed clear signs of edifice inflation, as informed by geodetic InSAR and GPS data. The InSAR analysis allowed us to identify changes in deformation patterns and localized accelerations, mainly in areas near the caldera and its interior. Finally, on November 17, 2025, IGEPN seismic stations registered a swarm of volcano-tectonic (VT) earthquakes on Fernandina’s northern flank, beginning with a 4.4 (MLv) earthquake. GPS stations showed co-seismic displacements, accompanied by significant deformation, also observed by InSAR (TerraSAR-X & Sentinel-1). Despite this sequence of signals, the seismic activity — 106 VTs located beneath the edifice —did not culminate in an eruption, as there were no lava flows nor detectable gases emitted to the surface. The inflationary pattern has diminished, but we remain attentive to further activity that could portend a future eruption, especially if there are MLv 4-5 VT events beneath the edifice. On previous occasions, these larger earthquakes have heralded an imminent eruption. Our next step is to model geodetic data to obtain a source model and its depth. While Fernandina Island is uninhabited, frequent tourist vessels pass by the shoreline to observe Galapagos wildlife and to observe lava flows entering the sea, as was the case in March 2024.
How to cite: Yepez, M., Mothes, P., Hernandez, S., Ruiz, M., Bell, A., LaFemina, P., and Aguaiza, S.: Geodetic and Seismic Observations of the 2025 Intrusion Event at Fernandina Volcano, Galapagos Islands, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15522, https://doi.org/10.5194/egusphere-egu26-15522, 2026.
Understanding the controls on magma ascent is critical for developing eruption forecasting. The movement of dykes (vertical magma intrusions) through the crust is particularly important to constrain, as often dyke propagation inferred from surface deformation, geodetic inversion techniques and seismicity is used to signify volcanic unrest, potentially leading to evacuation orders and eruption. However, the factors affecting dyke direction, geometry and ascent velocity are still relatively unconstrained.
In this study we explore the topographic loading controls on dyke behaviour. It is impossible to visualise dyke behaviour in natural systems as these processes occur at depth and on large scales, but scaled experimental analogue setups allow us to study the natural world in a laboratory setting, allowing us to make valuable insights into natural processes. We use an analogue setup, with a transparent, gelatine solid as a homogeneous elastic crust injected by dyed water from below as an intruding Newtonian fluid representing magma. The surface of the gelatine was moulded to represent a flat, inclined or ridge topography. Two CCD cameras placed above the experiment measure the vertical and lateral surface displacement created by the intrusion, as a penny-shaped experimental dyke grows. Polarised light is used in order to visualise the evolving stress field within the gelatine solid, recorded by an HD camera positioned at the side of the tank. Multiple injection points were used to vary the location of dyke initiation and their interactions with topography and previous injections. These experiments allow us to measure the 3D intrusion geometry, tip velocity, extent of surface deformation and rate, and relate these to the gelatine’s evolving internal stress field. Preliminary results indicate that topography does have an effect on dyke propagation, producing dyke bending, rotation and changing ascent velocity.
By understanding the topographic controls on dyke behaviour, we can better identify areas more likely to experience magmatic intrusions at volcanic systems worldwide, which has important implications for hazard mapping and managing volcanic risk.
How to cite: Willar-Sheehan, S., Kavanagh, J., and Williams, K.: How does topography affect the propagation of magmatic intrusions? An experimental study, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14970, https://doi.org/10.5194/egusphere-egu26-14970, 2026.
Coastal and submarine volcanoes are characterized by complex topographies, a significant portion of which lies below sea level, complicating efforts to fully quantify how surface geometry influences magma transport. Understanding the coupling between topography, stress fields, and magma propagation is essential for assessing volcanic hazards, including dike-fed eruptions and edifice instability.
Conventional models of dike propagation commonly approximate volcanic edifices as simplified surface loads, thereby neglecting the spatially variable stress perturbations introduced by realistic topography and bathymetry. To overcome this limitation, we develop a two-dimensional Boundary Element Model for fluid-filled fractures that explicitly incorporates a discretized free surface. This approach enables direct coupling between detailed topography and magma-driven deformation, allowing magma pathways to dynamically respond to surface geometry.
We implement the model geometry in COMSOL Multiphysics to compute stress under four representative scenarios: (1) a flat surface with an imposed surface load, (2) a symmetric volcanic edifice, (3) an asymmetric edifice, and (4) an asymmetric edifice subjected to an additional water load, with gravitational forces included in all cases. These end-member configurations are designed to isolate the effects of topography and water loads on magma propagation.
Preliminary results indicate that incorporating realistic topography significantly alters dike trajectories, fracture geometries, and associated stress and displacement patterns compared to simplified surface-load models. The presence of asymmetric topography and water loads further enhances stress heterogeneity, with implications for both magma ascent pathways and slope stability. These findings highlight the importance of explicitly resolving topography and marine loading when interpreting deformation signals and assessing hazards in coastal and submarine volcanic systems.
How to cite: Furst, S., Mantiloni, L., Maccaferri, F., Stoepke, F., Campbell, M., and Urlaub, M.: Impact of topography and water load on magma propagation modelling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7892, https://doi.org/10.5194/egusphere-egu26-7892, 2026.
Mount Pelée volcano (Martinique) is under unrest since 2019, characterized by an increase in shallow seismicity and surface deformation. To date, an explanation for this unrest is the presence of a shallow inflating source beneath the western flank of the volcano. The objective of this study is to develop more realistic mechanical models than those traditionally used to explain the observed deformation.
In this work, we investigate the mechanical stability of the volcanic edifice using Drucker-Prager elasto-plastic rheology. The mechanical model is constructed by interpolating topography and bathymetric data around the volcano over a distance of 30 km, with lateral boundaries set in free-slip, bottom face blocked and a free top surface. The elastic properties of the crust are derived from the P- and S-wave average velocities. We explore two extreme effective strengths of the crustal domain in the gravity field, as well as the response to a compliant shallow inflating source (30 MPa at 0 km depth).
Our models show that gravitational loading alone can reproduce the magnitude and pattern of the observed surface deformation. Progressively decreasing the effective crustal strength generates stress and deformation over distances larger than those observed with the geodetic measurements over the edifice, but compatible to what a giant landslide could produce. In addition, incorporating a shallow inflating source within the gravity field produces specific shear stress and strain patterns that also correlate with the observed seismicity during the unrest period, as well as surface deformation consistent with geodetic observations. Differentiating between gravitational or inflation-driven mechanisms requires higher-resolution geodetic and seismic observations.
Overall, our results indicate that the western flank of the volcanic edifice is prone to surface deformation and failure, while the eastern flank concentrates shear stress and strain at depth, highlighting potential hazard on both flanks. In this framework, deformation is primarily controlled by the strength parameters of the crust. Incorporating visco-plasto-elastic behavior with layered parameters consistent to a complete velocity model, together with inferred faults and landslide scars, should further improve our understanding of Mount Pelée’s mechanical behavior.
How to cite: Abboud Oropeza, A., Gerbault, M., Clouard, V., Chevrot, S., Plazolles, B., and Beauducel, F.: Mechanical stability of Mount Pelée volcano: insights from elasto-plastic numerical models., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10582, https://doi.org/10.5194/egusphere-egu26-10582, 2026.
Monitoring ground deformation induced by magma conduits at lava dome–building volcanoes provides key insights into magma ascent dynamics. Changes in dome growth rate are often associated with hazards such as increased explosive activity, dome collapse events, and pyroclastic flows. Timely detection and interpretation of precursory unrest are therefore vital for hazard assessment.
This study aims to elucidate the range of detectable conduit processes, inform the deployment of ground deformation monitoring infrastructure, and identify which conduit processes meet the detection criteria for measurement using high-resolution InSAR. We use 2D axisymmetric physics-based fluid dynamic models of magma ascent coupled to an elastic edifice to demonstrate how variations in shear stress and excess pressure on conduit boundaries generate ground deformation proximal to growing domes. Model scenarios are compared for three recent lava dome eruptions, highlighting key parameters controlling conduit-induced deformation, including syn-eruptive crystallisation, outgassing, initial conduit geometry, and magma composition.
The potentially long-lived and periodic nature of lava dome eruptions enables strategic deployment of ground-based monitoring infrastructure, such as tiltmeters, to improve observation of such events. This study provides a framework for assessing which transitions in conduit behaviour may be detectable, and over what distances from the conduit, by different geodetic methods.
How to cite: Eaton, E., Neuberg, J., and Ebmeier, S.: Magma conduit-induced ground deformation at lava dome–building volcanoes , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17871, https://doi.org/10.5194/egusphere-egu26-17871, 2026.
Rapid detection of the locations and movements of magma within the crust is essential for tracking volcanic unrests. The pressure exerted on the Earth's crust by magma migration causes ground deformation that can be measured by a variety of geodetic instruments. Consequently, the inversion of deformation signals allows the geometry and the position of the magmatic source to be inferred.
In the field of volcanic monitoring, the high temporal resolution of continuous Global Navigation Satellite System (GNSS) measurements makes them widely used for near real-time applications. However, traditional inversion techniques are usually time-consuming, model dependent, and often require a dense, well-distributed GNSS network, which is available only in a few volcanoes worldwide.
To overcome these challenges, machine learning provides efficient tools for emulating direct deformation models, accelerating the inversion process while modelling sources with complex geometries. Taking advantage of generalization capabilities of deep learning algorithms, we present a station-independent deep learning-based inversion framework that can instantly reconstruct underground magmatic causative sources from as few as ten GNSS stations without any prior knowledge of the station configuration or the target volcano.
Trained and tested on hundreds of synthetic deformation patterns, the deep learning-based inversion proves its potential and robustness in the retrospective application to the May 2008 eruption of Mount Etna as well as to Iceland's intrusive sequence between December 2023 and August 2024.
How to cite: Allegra, M., Cannavò, F., Currenti, G., Corsaro, M., Jousset, P., Palazzo, S., and Spampinato, C.: A deep learning framework for rapid inversion of ground deformation to model volcanic sources, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19488, https://doi.org/10.5194/egusphere-egu26-19488, 2026.
The Late Pleistocene Lower and Upper Acıgöl Tuffs (LAT and UAT; 190 ± 11 ka and 164 ± 4 ka) represent the two most recent major ignimbrite eruptions on the Cappadocia Plateau in the Central Anatolian Volcanic Province. Both Acıgöl ignimbrite eruptions correspond to VEI 6 events, with caldera collapse and regionally widespread dispersal of tens of km³ of tephra. Understanding syn-caldera eruptive processes is critical for volcanic hazard assessment in regions such as Cappadocia, where active volcanic systems coexist with dense populations and intense tourism. Although previous studies of the Acıgöl caldera complex have constrained eruption ages, stratigraphy, and geochemistry, the latest syn-caldera eruptive processes associated with UAT ignimbrite emplacement remain poorly resolved. Here we reconstruct the eruptive history of the UAT through proximal volcanostratigraphy, integrated with glass geochemistry and previous published geochronology. The stratigraphic record within the caldera documents a continuous succession of deposits including a phreatomagmatic tephra ring, debris-avalanche deposits derived from the Koçadağ intra-caldera dome, lithic-rich Plinian fallout, caldera-forming ignimbrite, and post-collapse lava-dome emplacement. Our results indicate that the Taşkesik intra-caldera maar eruption occurred during the early stages of the UAT caldera-forming eruption. While not a deterministic precursor, this small-scale event could represent the onset of a cascade of processes that ultimately led to magma chamber decompression, roof subsidence, and ignimbrite emplacement associated with caldera collapse. This refined syn-caldera framework at Acıgöl provides new constraints on caldera-collapse dynamics and has direct implications for hazard assessment in active caldera systems.
This work was funded by the Spanish Ministry of Science and Innovation (TURVO, PID2023-147255NB-I00; MCIN/AEI/10.13039/501100011033), the EU (ERDF; Horizon 2020–MSCA PÜSKÜRÜM, Grant 101024337), and the Italian PNRR–NextGenerationEU through the ÇoraDrill project (CUP B83C25001180001).
How to cite: Bolós, X., Sunyé-Puchol, I., Özsoy-Ünal, R., Akkas, E., Muir, L., Tavazzani, L., Nazzari, M., Bachmann, O., Scarlato, P., and Mollo, S.: Upper Acıgöl Tuff: Eruption dynamics of the youngest Cappadocian ignimbrite, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13293, https://doi.org/10.5194/egusphere-egu26-13293, 2026.
How to cite: Novoa, C. and Hooper, A.: Decoding temporal deformation patterns: From Magma Triggers to Mush Dynamics , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19366, https://doi.org/10.5194/egusphere-egu26-19366, 2026.
Posters virtual: Thu, 7 May, 14:00–18:00 | vPoster spot 3
EGU26-3001 | Posters virtual | VPS25
Thermo-Poro-Elastic effects as hidden drivers of gravity signals in volcanic systemsThu, 07 May, 15:03–15:06 (CEST) vPoster spot 3
Gravity observations are widely used in volcanic monitoring to infer subsurface mass redistributions, commonly interpreted in terms of magma intrusion. However, gravity changes may also arise from thermo-poro-elastic (TPE) processes associated with temperature and pore-pressure variations in fluid-saturated reservoirs. Neglecting these effects can lead to ambiguous or misleading interpretations of gravity signals during volcanic unrest.
The recent development of TPE inclusion models allows us to describe the mechanical fields induced by fluid-saturated rock volumes undergoing pore-pressure and temperature variations. These sources can coexist with magmatic sources within volcanic systems and are typically located at shallower depths than the deep magmatic reservoir, which acts as the primary engine by releasing hot fluids. These exsolved fluids rise from depth and either accumulate in, or migrate through, overlying brittle rock volumes, which respond to thermal and pore-pressure perturbations and therefore act as secondary sources of deformation and gravity change. In this work, we consider a disk-shaped TPE inclusion, a geometry that has been successfully applied in previous studies to represent deformation fields that are predominantly radial and associated with axisymmetric sources.
The results show that gravity variations induced by a TPE inclusion depend strongly on the fluid phase. Both liquid water and gaseous fluids can produce the same significant ground uplift, but lead to different gravity residuals: negative for liquid water and minor but positive for gaseous fluids. In contrast, condensation or vaporization of a thin layer near the surface can generate large gravity changes without notable deformation. As a result, heating and pressurization of a TPE inclusion can mask or weaken the gravitational signature of magma ascent, complicating the interpretation of gravity data and highlighting the need to account for hydrothermal effects when estimating magma volumes during unrest.
Gravity data collected over the past decades at the Campi Flegrei caldera (Italy) provide an ideal test site for applying our model and offer intriguing insights into both past and current unrest phases, although our results are applicable to any volcanic system with an active hydrothermal system. These findings highlight the importance of incorporating TPE effects into gravity data interpretation and integrated volcano monitoring strategies. Accounting for them improves our ability to distinguish between magmatic and hydrothermal contributions, leading to more robust assessments of subsurface dynamics and volcanic hazards.
How to cite: Nespoli, M., Bonafede, M., and Belardinelli, M. E.: Thermo-Poro-Elastic effects as hidden drivers of gravity signals in volcanic systems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3001, https://doi.org/10.5194/egusphere-egu26-3001, 2026.
