This session invites contributions from researchers in volcano seismology, infrasound, and related fields, focusing on (i) seismicity and infrasound catalogues and their spatio-temporal evolution, (ii) wave propagation, scattering, and atmospheric effects, (iii) high-resolution imaging of volcanic structures, (iv) joint seismic–acoustic source inversions, and (v) time-lapse monitoring and forecasting. Studies on geothermal analogues, novel instrumentation, and emerging analysis methodologies (e.g., machine learning) are also welcome. By fostering cross-disciplinary dialogue between seismologists, acoustic specialists, and numerical modellers, this session aims to highlight recent advances and key challenges in characterizing volcanic processes and improving hazard assessment
Orals: Wed, 6 May, 16:15–18:00 | Room 0.96/97
Volcano seismology and acoustics have advanced rapidly in recent years, significantly improving our ability to observe and interpret volcanic processes across a wide range of spatial and temporal scales. This talk will provide a broad overview of currently relevant topics in these fields, with an emphasis on how seismic and acoustic observations jointly constrain magma, gas, and fluid dynamics within volcanic systems. Key themes include evolving interpretations of volcanic tremor, long-period seismicity, and infrasound as expressions of coupled conduit flow, degassing, and fragmentation processes. The growing use of dense seismic and infrasound arrays has enabled improved source localization and characterization, particularly during explosive and transitional eruptive activity, and improved tomographic characterization of trans-crustal magmatic systems. Data-driven approaches, including machine learning, are increasingly applied to detection, classification, and forecasting, complementing physics-based models that link observed signals to underlying processes. This talk will also highlight the expanding role of volcano acoustics, from near-field infrasound and resonance phenomena to atmosphere–volcano coupling, alongside advances in sensor technology and deployment strategies. Finally, I will also discuss implications for hazard assessment and operational monitoring, emphasizing the value of integrated, interdisciplinary approaches and expanded monitoring in understudied volcanic regions.
How to cite: Roman, D.: Listening to Volcanoes: Current Frontiers in Volcano Seismology and Acoustics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11755, https://doi.org/10.5194/egusphere-egu26-11755, 2026.
Rincón de la Vieja is a complex stratovolcano characterized by a persistently active magmatic-hydrothermal system that hosts a hyperacid crater lake with a long record of phreatic and phreatomagmatic activity. This study synthesizes volcanic behavior from 2014 to 2025 using continuous seismo-acoustic monitoring, supported by detailed eruption chronologies, analysis of discrete seismic signals (VTs, tornillos, LPs, banded tremor, and VLPs), and identification of pre-eruptive trends. By combining these observations with ground deformation and SO2 emission measurements, we characterize the evolution of the magmatic–hydrothermal systems .
Results suggest a shift from a mineralogically sealed system to repeated episodes of conduit opening, culminating in the lowest crater-lake levels observed in the past 20 years in May 2024. We propose two dominant processes governing major eruptive episodes: 1) the buildup of magmatic gases beneath a shallow sealing zone and 2) variations in permeability within the magmatic-hydrothermal system. Both mechanisms regulate eruptive intensity and account for elevated gas output despite declining eruptive energy. The interaction of these processes also defines the primary volcanic hazards, particularly lahars and pyroclastic density currents. This integrative approach enhances our overall understanding of wet volcanic systems and offers a practical framework for improving monitoring strategies, eruption forecasting, and hazard mitigation at highly active volcanoes such as Rincón de la Vieja.
How to cite: Bakkar Hindeleh, H., Caudron, C., Illsley-Kemp, F., Pacheco, J. F., van der Laat, L., Taylor, W., Alvarado, G. E., Mora, M. M., de Moor, J. M., Salas-Navarro, J., Rodríguez, A., Muller, C., Avard, G., and Martínez, M.: An Overview of Seismo-Acoustic and Eruptive Activity at Rincón de la Vieja Volcano, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18405, https://doi.org/10.5194/egusphere-egu26-18405, 2026.
Eruptions at continental basaltic volcanoes can take and combine various forms, including lava lakes, lava flows and fountaining, explosions or structural collapses. Recording seismicity is widely recognized as essential for tracking magma movements at depth but must be complemented with other observations for monitoring eruptions, which are by essence atmospheric processes. Aside from a few well-instrumented cases worldwide, accurately reconstructing the precise eruptive mechanisms and chronology is hampered by the lack of detailed visual observations in space and time. However, because they emit low-pitched inaudible sounds, called infrasounds, any changing and potentially hazardous eruptive activity can be inferred with specialised microphones.
On 22 May 2021 in D.R. Congo, the drainage of Nyiragongo’s long-lived and world’s largest lava lake was accompanied by lava flows from eruptive fissures toward a one-million urban area composed of the cities of Goma (D.R. Congo) and Gisenyi (Rwanda). After 1977 and 2002, this was the third known flank eruption and the first one adequately monitored with seismic and geodetic instruments to understand magma movements at depth. A probable scenario supported by these geophysical observations is the rupture of the edifice, starting around 15:57 UTC, draining the lava lake during a short-term (~6 hours) flank eruption and initiating a week-long magmatic intrusion (dyke) in the Earth’s crust.
Using acoustic numerical modeling, we converted infrasound records from local distance (< 20 km) up to Kenya (more than 800 km away from Nyiragongo) into high-resolution time-lapse observations of this catastrophic lava-lake drainage. The emitted infrasounds also provided unprecedented insights into the timing of fissure openings and lava eruptions on the volcanic flank, occurring simultaneously with the lava lake drainage. This striking example highlights how decoding each specific volcano’s acoustic signature provides unique information inaccessible to other ground-based instruments, which can be integrated to monitoring and multi-hazard early warning systems.
How to cite: Barrière, J., Oth, A., Assink, J., d'Oreye, N., and Evers, L.: The details of the 2021 Nyiragongo eruption using infrasound, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10062, https://doi.org/10.5194/egusphere-egu26-10062, 2026.
Ruapehu is one of the most active volcanoes in Aotearoa New Zealand, with over 100 eruptive events over the last 135 years. In 2022, the volcano underwent a significant period of unrest which included a new heating phase in the summit crater lake, increases in gas emissions, and strong levels of seismic tremor, the most intense observed at the volcano for nearly 30 years. The tremor was also notable for featuring a sequence of highly-periodic low frequency “drumbeats”. Both tremor and drumbeats were hypothesised to originate from within a shallow hydrothermal system but a sparse seismic network precluded accurate location information. Here we utilised the network covariance matrix approach to map the location of tremor within the Ruapehu volcanic system before and during the 2022 unrest episode. We find low level tremor is detectable up to three months before the unrest begins, beginning shortly before a small sub-summit earthquake swarm approximately 3 - 4 km below the summit. Tremor during the unrest period is primarily located at shallow depths, within 500 m of the summit vent, suggesting a mechanism within the shallow hydrothermal system. This study was the first to apply the network covariance method for studying tremor at Ruapehu and demonstrates the technique’s value as an effective tool for real-time volcanic tremor monitoring in Aotearoa New Zealand.
How to cite: Lamb, O., Reiss, M., Illsley-Kemp, F., Bramwell, L., Moutell, C., Caudron, C., and Yates, A.: Tracking Tremor and Drumbeat Locations during the 2022 Unrest Episode of Ruapehu volcano, Aotearoa New Zealand, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14232, https://doi.org/10.5194/egusphere-egu26-14232, 2026.
Volcano observatories often rely on their ability to accurately decipher volcano-seismic signals to assess the state of a specific volcanic system. For this purpose, well-established patterns such as VT and LP event sequences during pre-eruptive unrest phases – or their periodic manifestation as ‘drumbeats’ – constitute a trusted and reasonably well-understood parameter. We present a suite of similarly distinct, but less commonly observed periodic patterns recorded at various volcanic systems, notably consisting of stable and dynamic drumbeat-like seismicity, as well as pulsed and spiked tremor episodes. Within that, we focus on a long-term pulsed tremor signal recorded during a rare dome-extrusion phase at Whakaari/White Island (New Zealand). Considering the resemblance between this and other instances of pulsed tremor observed at comparably phreatic systems in Indonesia and Costa Rica, we interpret the occurrence of such periodic seismicity as the mechanical response of partially sealed hydrothermal systems upon the influx of magmatic and non-magmatic fluids. These often short-lived patterns are very hard to trace using conventional Volcano Observatory monitoring tools, such as EQ detectors and tremor-based metrics (e.g., RSAM, SSAM, DSAR), and their significance for volcanic hazard assessment is largely unknown. As Machine Learning techniques are becoming increasingly accessible, we explore in how far they constitute an opportunity to track these elusive seismic patterns. Using this case study as a starting point, we push towards further investigation of similar periodic signals and their underlying physical source processes. We seek to discuss how common such subtle patterns are, and how they can be detected and interpreted within their respective volcano-environmental contexts.
How to cite: Steinke, B., Caudron, C., and Cronin, S.: More than a drumbeat – Towards a new suite of periodic patterns in volcano-seismology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13414, https://doi.org/10.5194/egusphere-egu26-13414, 2026.
The 2014-2015 Bárðarbunga dike intrusion and caldera collapse, leading to the six-month Holuhraun eruption, featured more than 80 recurring Mw ≥ 5 earthquakes located on the caldera ring fault. The caldera floor, covered by the Vatnajökull ice cap, subsided by 65 meters during the eruptive period. Continuous monitoring using an extensive seismic network has shown evidence of fault slip reversal and repeating earthquakes. The sequence of moderate-sized ring fault earthquakes resumed in 2017, suggesting a continuation of the same type of fault slip behaviour in response to the reversal of the collapse.
We re-examine the data prior and post fault slip reversal in the 2014-2016 period to improve our understanding of the processes governing the recurring earthquake sequence observed since the eruption starting in 2014.
We use the seismic data collected since 2014 to build a new earthquake catalogue for the caldera ring fault. We use template matching to detect previously undetected low magnitude earthquakes. We developed a tailored data processing pipeline, leveraging the Icelandic HPC computing cluster and its GPU nodes, to optimize template matching and earthquake cross correlations, with an emphasis on finding repeating earthquakes on the caldera ring fault. We additionally carry out double difference relocation.
We present an enhanced earthquake catalogue for the 2014-2016 period, with particular focus on the post-eruptive fault slip reversal, including a repeating earthquake analysis. We achieve a fourfold increase in the number of events in the catalogue and can detect events up to 1 ML lower than the input catalogue. Using parallelisation, we can speed up our processing by up to 16 times on the HPC clusters. With new better-constrained catalogues generated using dense temporary networks from recent field campaigns, we are working towards improving locations for catalogues based on older data using double-difference relocation techniques.
When the resurgence period is included, the Bárðarbunga caldera collapse event has effectively lasted for almost 12 years and includes more than 100 Mw ≥ 5 earthquakes. Re-examining older data with state-of-the-art processing techniques and computing resources offers a unique opportunity to build further context and aid holistic interpretation for the on-going events at the caldera, as well as to increase our broader understanding of faults undergoing large slip movements and the evolution of caldera collapse cycles.
How to cite: de Vries, Y. A., Heimisson, E. R., and Winder, T.: An enhanced catalogue of ring fault seismicity at Bárðarbunga caldera since the start of the 2014 Holuhraun eruption , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11324, https://doi.org/10.5194/egusphere-egu26-11324, 2026.
Volcanic seismicity is a powerful indicator of activity at volcanoes worldwide, providing information on volcanic structures and subsurface processes such as magmatic fluid transport. Volcanic systems produce a range of eruptive styles and durations; determining whether future eruptions will be explosive or effusive is key for reducing the hazards faced by local communities. Mt. Etna is the largest volcano in Europe and is continuously monitored by a substantial seismic network providing an ideal location to quantitatively constrain links between eruptive styles and seismicity.
During periods of intense volcanic activity, many seismic events will go undetected. A matched filter search identifies repeats of template events, including those which are hidden behind the noise, and can increase a seismic catalogue by a factor of 10. Additionally, it categorises seismic events into families of similar waveforms, implying shared source characteristics and locations. This establishes a framework for investigating how seismic sources evolve that can be linked to subsurface processes and structures, providing a quantitative comparison with the vast and complex eruptive history of Mt. Etna.
Here we focus on the December 2018 flank eruption at Mt Etna, using template events from INGV’s seismic catalogue for a matched filter search across four years of continuous data. We investigate spatial, temporal and waveform trends of individual families, to track how the seismic signal evolves over time - providing a quantitative framework to interpret subsurface processes and eruptive styles at Mt. Etna. Initial results highlight several families that are triggered during different stages of the eruption, coincident with variations seen in GPS and gas emissions during this time frame. This categorisation of seismicity allows finer details to be unveiled that were previously not seen in the original seismic catalogue.
How to cite: Eyles, J., Frank, W., Poli, P., and Alparone, S.: How do temporal patterns in volcanic seismicity relate to the dynamics between volcanic processes at Mt Etna?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19356, https://doi.org/10.5194/egusphere-egu26-19356, 2026.
Mt. Etna volcano is Europe’s most active volcano, showing pre- and co-eruptive seismic signals as tremor and long-period (LP) events. Understanding those signals contributes to hazard assessment and risk management during volcanic eruptions. In our study we examine the wavefield composition of LP events and volcanic tremor on Mt. Etna. Both are characteristic seismic signals generated by fluid-driven volcanic activity. By combining results from a seismic array and a rotational sensor co-located with a seismometer (6C station), we decipher their wavefield.
For seismic data from August - September 2019 we calculate and compare directional and phase velocity estimates. Back azimuths (BAz) of LP events and tremor from the seismometer array and the 6C station are compared to reference network BAzs which are obtained from locations estimated by the Istituto Nazionale di Geofisica e Vulcanologia-Osservatorio Etneo (INGV-OE) on Mt. Etna.
We observe varying seismic tremor and surface activity which we associate with different eruption phases. During these tremor phases, either the array or 6C BAz estimates agree well with the INGV-OE reference. LP event BAz directions from both methods show a southward shift in comparison with the INGV-OE reference. Local heterogeneities might cause the larger southward deviation of the 6C BAz results in comparison with the array.
Array slowness results indicate that tremor and LP events were primarily composed of surface waves. Rotational sensor recordings further indicate a wavefield dominated by SH-type waves. Together with the array results, this suggests a Love-wave dominated wavefield. The combination of rotational sensors with seismic arrays significantly enhances our ability to constrain the wavefield in complex volcanic settings.
How to cite: Vesely, N. I. K., Eibl, E. P. S., Currenti, G., Sciotto, M., Di Grazia, G., Ohrnberger, M., and Jousset, P.: Distinguishing the wavefield of volcano-seismic events on Mt. Etna: Achieving wavefield separation combining a seismic array and a rotational sensor, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9631, https://doi.org/10.5194/egusphere-egu26-9631, 2026.
Episodes of volcanic tremor provide valuable insights into subsurface processes at active volcanoes, yet the physical origin of temporal variations in tremor spectra remains debated. Previous work at Mt. Etna (Italy) demonstrated a strong correlation between relative frequency changes (df/f) during broadband volcanic tremor and seismic velocity changes (dv/v) derived from passive seismic interferometry. Such correspondence suggests that tremor spectra are responding to changes in medium properties rather than variations in the tremor source.
Here, we extend this observation beyond Etna to include Tungurahua volcano (Ecuador) and Rincón de la Vieja volcano (Costa Rica). At both volcanoes, we observe consistent correlations between df/f extracted from broadband tremor and dv/v. At Tungurahua, these changes are linked to earthquake-induced damage and meteorological processes, once again suggesting that their modulation reflects changes in the phase velocity within near-surface layers.
The persistent relationship between dv/v and df/f at both Tungurahua and Rincón de la Vieja not only supports previous interpretations at Etna, but shows that such a relationship is present across varied volcanic systems. This strengthens the case for using df/f during broadband tremor as a proxy for tracking subsurface changes within volcanic systems, particularly where using traditional methods may be challenging. Furthermore, our results highlight the need to clarify the respective roles of source, path, and site effects in shaping the recorded seismic wavefield in volcanic environments. Doing so avoids misattributing spectral changes as source-driven, and opens the door to exploiting tremor spectra for monitoring purposes.
How to cite: Yates, A., Caudron, C., Hidalgo, S., Battaglia, J., Zuccarello, L., De Angelis, S., Bakkar Hindeleh, H., and Taylor-Castillo, W.: Multi-volcano observations of coupled tremor spectra and subsurface velocity changes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7373, https://doi.org/10.5194/egusphere-egu26-7373, 2026.
The spectral stability commonly observed in volcanic tremor signals is usually interpreted as reflecting a stable source mechanism. In this study, we investigate the role of seismic wave propagation within a magmatic plumbing system derived from thermoelastic simulations, using 2D elastic numerical simulations based on the Spectral Element Method. The modeled medium is grounded in the most recent understanding of the thermo-mechanical effects of magma injections into crustal rocks. Our wave propagation simulations demonstrate that such structures generate strong seismic wave scattering. We identify two primary mechanisms responsible for spectral stability and for generating a characteristic spectral signature: the interference of multiply scattered waves along the source-receiver paths, and the trapping of waves within the volcanic structure. In the latter case, we show that wave trapping can lead to local resonance and that its spectral signature appears clearly in the coda of volcanic signals. The observed link between frequency content and the elastic and scattering properties of the source region implies that structural changes may be characterized through the study of the spectral characteristics of volcanic recordings and their variations. Overall, our findings emphasize the fundamental importance of multiple seismic wave scattering in volcanic environments.
How to cite: Bracale, M., Campillo, M., Shapiro, N. M., Brossier, R., and Melnik, O.: Multiple Scattering of Seismic Waves in a Heterogeneous Magmatic System and Spectral Characteristics of Long Period Volcanic Earthquakes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5530, https://doi.org/10.5194/egusphere-egu26-5530, 2026.
Posters on site: Fri, 8 May, 10:45–12:30 | Hall X2
The search for reliable eruptive precursors is a central challenge in volcano monitoring, essential for optimizing volcanic early-warning systems. Recent studies have shown that the Shannon entropy of seismic signals is a promising precursor, capable of forecasting imminent eruptions with high reliability. In addition, cross entropy computed between pairs of seismic stations can help pinpoint the location of an impending eruptive vent.
In this study, we analyse the behaviour of these two entropy measures for the Island of Hawai‘i from 2017 to 2025. We examine eruptions from both Mauna Loa and Kīlauea, yielding forecast lead times of 30 minutes to 24 hours. Differences in these lead times may reflect the complexity of the volcano-structural setting of the island and its underlying volcanic plumbing systems. Highly fractured areas may favour rapid magma ascent, leading to a short eruption warning. Heat maps of cross-entropy across all station pairs in the network enabled precise forecasting of the locations of forthcoming eruptive sources, except when the new vent formed outside the seismic network.
How to cite: Santos Campos, I., D'Auria, L., Álvarez-Hernández, A., Rey-Devesa, P., Ibáñez, J. M., Prudencio, J., Titos, M., and Benítez, C.: Shannon Entropy as an eruptive precursor: a practical study on Hawai‘i Island from 2017 to 2025, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-388, https://doi.org/10.5194/egusphere-egu26-388, 2026.
Kīlauea, Hawaii, one of the world's most active volcanoes, has experienced numerous (>40) eruptive episodes since December 2024 with remarkable lava fountain heights (up to 450m) in Halemaʻumaʻu crater. Following a dike intrusion within the Halemaʻumaʻu crater in December 2024, the eruption entered a stable pressurization and release pattern from January 2025 onwards with lava flows during the sequence confined to Halemaʻumaʻu crater.
We study the 2024-26 sequence focusing on relative seismic velocity changes (dv/v). We use ~20 seismic stations located within 10 km of the Halemaʻumaʻu crater and process the data using the traditional cross-station and less conventional single-station approach and estimate the dv/v using the wavelet approach. The dv/v patterns highlight at least three distinct phases of activity during the 2024-26 eruption sequence, as well as some interesting velocity decreases prior to the onset of the sequence in December 2024 although these are spatially confined.
We inspect the differences between our new results with previous seismic velocity patterns (2015-2024) and explore the nature of the changes using complementary observations (seismic and geodetic data), as well as numerical modeling. Our study suggests a change in strain patterns at the shallow Halemaʻumaʻu reservoir which implies a dynamic evolution of the magmatic system feeding the eruption. Additionally, we show how deformation (deflation) of the deeper South Caldera reservoir contributes to the observed dv/v patterns. Our study sheds light on the dynamics between different magma reservoirs and links to surface processes.
How to cite: Caudron, C., Reiss, M. C., Bennington, N., Hotovec-Ellis, A., Rohnacher, A., Lanza, F., Sens-Schönfelder, C., Jolly, A. D., Roman, D., Wauthier, C., Lo, A. W. K., Anderson, K., and Flinders, A.: Seismic velocity changes during the 2024-26 fountaining sequence at Kīlauea, Hawaiʻi, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17603, https://doi.org/10.5194/egusphere-egu26-17603, 2026.
The ongoing (2024-) eruption sequence at Kīlauea Volcano, Hawai’i, has comprised 40 (as of mid-January, 2026) episodes of high fire fountaining, as well as episodes of dome fountaining, effusive eruption, and gas pistoning (series of cyclical overflows and drain-back of lava). While many episodes of gas pistoning are visually apparent in webcam footage, seismic characterization of gas pistoning and VLP swarms allows for an objective analysis of pistoning frequency, amplitude, and duration, providing greater insight into the gas ascent and escape process and its relationship to fire fountaining episodes. We thus analyze continuous RSAM to quantify the timing, duration, frequency, and amplitude of gas pistoning throughout the 2024-2026 eruption sequence and its relationship to fire fountain heights and durations.
Gas pistoning was first observed in March of 2025 as an immediate precursor to fire fountaining, and post-March fire fountains have generally been preceded by gas pistoning. The onset of precursory gas pistoning corresponds to a shift to shorter-lived fire fountains, suggesting that precursory gas pistoning contributes to the duration of fire fountain episodes. However, beginning in late May, gas pistoning became more decoupled from high fountaining, with a marked delay between the end of gas pistoning and the high fountain onset. The fountains that follow a delay after pistoning are among the highest in the eruption sequence, suggesting that a short-term sealing of gas pathways contributes to greater fountain heights. The most recent (November 2025 onwards) episodes of fire fountaining have also been followed by swarms of repeating VLP events or by additional gas-pistoning tremor, suggesting ongoing gas escape following the end of high fire fountaining. Overall, seismic observations indicating increased precursory and post-fountaining degassing suggest increasing degrees of vertical connectivity in Kīlauea’s magma transport system.
How to cite: Roman, D., Reiss, M., and Caudron, C.: Seismic characterization of pre- and post-fountaining phenomena during the 2024-2026 Kīlauea eruption sequence, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14959, https://doi.org/10.5194/egusphere-egu26-14959, 2026.
In 2014-15, the subglacial Bárðarbunga caldera collapsed, subsiding 65 metres as magma flowed out from beneath it to feed a fissure eruption at Holuhraun. Subsequently, the caldera has been re-inflating, indicating recharge of the crustal magma reservoir. Sustained seismicity along the caldera ring faults – but with reversed focal mechanism polarity compared to the eruption period – further supports its ongoing resurgence. In summer 2021, 2024 and 2025 we installed temporary broadband seismic arrays on the ice cap above Bárðarbunga, to provide improved constraints on earthquake hypocentres and focal mechanisms.
We use QuakeMigrate to produce catalogues of microseismicity, with 8,500 and 19,500 events located in the campaigns in 2021 and 2024, respectively. The magnitude of completeness, MC is ~ -1. Relative relocation reveals a sharply defined ring fault, consistent in geometry with geodetic constraints obtained during the 2014-15 collapse, thus providing strong evidence that the same structure is being reactivated as the caldera re-inflates. Tightly constrained focal mechanisms show excellent agreement with the local ring-fault geometry defined by the relocated microseismicity, and steep dip-slip faulting corresponding to uplift of the caldera floor. Low frequency earthquakes observed between 15 - 25 km depth in the normally ductile part of the crust below Bárðarbunga, and at around 6 km depth below the caldera, signify activity in the deeper plumbing system of the volcano, which may indicate magma ascent pathways. These events contribute to excellent ray coverage for tomography, which we will use to image the shallow melt reservoir and its geometry relative to the ring-fault.
How to cite: Winder, T., Heimisson, E. R., Rawlinson, N., Brandsdóttir, B., Jónsdóttir, K., and White, R. S.: High-Resolution Microseismicity Provides Insights into Ring-Fault Geometry at the Re-inflating Bárðarbunga Caldera, Iceland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1110, https://doi.org/10.5194/egusphere-egu26-1110, 2026.
Monitoring seismic velocity variations in the shallow crust using noise-based techniques has emerged as an effective approach for tracking temporal changes in the local stress field. Despite their potential, real-time implementations of these methods have so far been mostly restricted to volcanic areas and are operational at only a limited number of volcano observatories due to the relative simplicity and speed of application in those contexts. In this work, we present the first real-time monitoring of seismic velocity variations applied to a tectonic seismic swarm in the Aegean Sea, which initiated on January 31, 2025. We introduce objective and rapid procedures to identify the key parameters necessary for the analysis and to compute the probability that new observations belong to the same statistical distribution as the background, allowing us to highlight potential anomalies as they occur. Finally, we interpret the processes driving the Aegean seismic swarm and suggest the presence of distinct recovery patterns in relative velocity variations following the abrupt drops typically observed during co-seismic effects.
How to cite: Mandler, E., Zaccarelli, L., Faenza, L., and Melis, N.: Real-time monitoring of seismic velocity variations during the 2025 Aegean Sea seismic swarm, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19911, https://doi.org/10.5194/egusphere-egu26-19911, 2026.
Taupō volcano is a frequently active rhyolitic caldera volcano in the central North Island of Aotearoa New Zealand that was the site of Earth’s most recent supereruption (Ōruanui, ∼25.5 ka), as well as one of the most violent eruptions globally of the last 5000 years (Taupō, 232±10 CE). Taupō has erupted 28 times since the Ōruanui event and displays unrest activity (seismicity and surface deformation) on roughly decadal timescales. In 2022–23, Taupō volcano underwent a period of unrest with elevated levels of earthquakes and ground deformation, including a M 5.7 earthquake that caused a tsunami within Lake Taupō. This elevated activity resulted in the Volcanic Alert Level for Taupō being raised to Level 1 for the first time. Here, we present results from a detailed characterisation of the activity beneath Taupō throughout the year-long unrest episode including a catalogue of earthquake locations; relative relocations; magnitudes; and focal mechanisms. We focus particularly on the detail in the catalogue that reveal the processes, state and structure of the modern magma reservoir beneath Taupō and builds our ability to interpret future unrest and possible eruption at the volcano.
How to cite: Mestel, E., Illsley-Kemp, F., Savage, M., Wilson, C., and Hreinsdóttir, S.: Characterisation of the 2022–23 unrest episode at Taupō volcano, Aotearoa New Zealand, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14560, https://doi.org/10.5194/egusphere-egu26-14560, 2026.
Seismograms recorded near active volcanoes contain numerous volcanic earthquakes and tremors that capture signatures of diverse volcanic processes and offer insights into the state of the volcano’s plumbing system and its underlying physical mechanisms. However, the strong variability of the seismo-volcanic signals makes their interpretation in terms of associated physical processes difficult. To address this, we employ unsupervised machine learning techniques, specifically, the scattering transform and Uniform Manifold Approximation and Projection (UMAP), to extract statistically significant features from continuous seismograms and to identify meaningful patterns related to volcanic activity. This approach eliminates the need for discrete event catalogs, enabling a comprehensive analysis of seismic manifestations of the volcanic activity.
Our study focuses on Piton de la Fournaise (PdF), a highly active basaltic volcano on La Réunion island, France, which erupted 25 times between 2014 and 2024. As one of the world’s best-monitored volcanoes, PdF represents an ideal natural laboratory for testing and refining our methodology. We analyze three-component seismograms from multiple stations and validate our findings using complementary datasets, including eruption, earthquake, and tremor catalogs.
The two-dimensional UMAP representation of the analyzed seismic data reveals distinct patterns that correlate with volcanic activity. The resulting seismogram atlas shows isolated clusters of points forming continuous features, which correspond to co-eruptive tremors. During non-eruptive periods, the analyzed time windows accumulate in a dense point cloud. Within this cloud, a predominantly random distribution of points is evident. However, some points form nearly linear, continuous pathways within the cloud, correlating with periods of magmatic intrusions. Adjacent to the dense point cloud, pre-eruptive seismic swarms are grouped in a specific region of the UMAP space, suggesting a common underlying mechanism.
How to cite: Gärtner, M. A., Campillo, M., and Shapiro, N.: Unsupervised Machine Learning for Analyzing Continuous Seismic Recordings: Insights from Piton de la Fournaise Volcano, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7083, https://doi.org/10.5194/egusphere-egu26-7083, 2026.
Imaging volcanic interiors is of paramount importance for understanding volcano-seismic signals and their underlying sources. However, determining fine scale structure in highly heterogeneous media is a significant challenge using traditional imaging approaches. Furthermore, modelling and inversion tools often employ cumbersome and lengthy procedures, which can be slow to implement, especially during volcanic crises when results are needed swiftly as large data volumes arrive at Volcano Observatories. Machine-learning (ML) methods, which have experienced rapid growth over the last decade, have strong potential to address this challenge due to their suitability for complementing physics-based numerical simulations and inversion. In particular, we examine the feasibility of imaging small-scale heterogeneities beneath volcanoes, such as propagating individual dykes, directly from seismic data using rapid ML-based imaging.
Here we build on previous work where a large suite (> 5000) of seismic earthquake gathers (i.e. seismic records from individual earthquakes) derived from numerical simulations in highly heterogeneous 2D velocity models, were used to train a Fourier Neural Operator (FNO). Subsequently that FNO was used to invert for complex structure in previously unseen geologically realistic 2D models. As the training procedure is extremely computationally expensive, and is likely prohibitive in 3D, here we ask: “can meaningful information be retrieved from seismic data derived from 3D simulations, based on an FNO that was trained only on 2D seismic data”? We see the answer to this question as important, as it helps determine the nature of the FNO training required in order to apply this new methodology beyond the numerical domain into the 3D physical world.
We build 3D models that are consistent with the 2D models used for machine learning training. Seismic data are generated from these models, and we evaluate how well a 2D pre-trained algorithm can recover geological structures and velocity characteristics from the 3D data.
How to cite: Evans, C., Lokmer, I., Bean, C., and Totten, E.: Direct seismic data inversion for volcanoes using machine learning: a comparison of 2D and 3D cases, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10295, https://doi.org/10.5194/egusphere-egu26-10295, 2026.
This research employs a Random Forest machine learning method to forecast eruption probability for three Indonesian volcanoes: Semeru, Lewotobi Laki-laki, and Ruang. The primary objectives are to (1) evaluate model performance under varying data quality conditions and (2) test the transferability of forecasting models between different volcanic systems. We compare three scenarios: Semeru's major eruptions (December 2020 and 2021) with significant data gaps, Lewotobi Laki-laki's seven major eruptions (March - August 2025) with high data completeness, and Ruang's eruption (April 2024).
Seismic data from the vertical component (Z) were processed using Real-time Seismic Amplitude Measurement (RSAM), Displacement Seismic Amplitude Ratio (DSAR), and MSNoise to monitor seismic amplitude variations and relative velocity changes. Statistical methods extracted an initial set of 768 features from these processed signals. After removing highly correlated features, the top 20 most relevant features were selected for model training.
For Semeru, a model trained on the 2020 eruption successfully forecasted the 2021 eruption, with forecast probability exceeding the 0.7 threshold 12 hours prior to the eruption. For Lewotobi Laki-laki, models trained on earlier eruptions (March-April 2025) successfully forecasted subsequent event in May 2025, achieving lead times ranging from 6 hours to 1 day. Cross-volcano testing revealed that the Semeru-trained model failed to forecast the Ruang eruption, likely due to data incompleteness. In contrast, the Lewotobi Laki-laki model successfully forecasted the Ruang eruption 6 hours in advance, demonstrating successful model transferability. These results highlight the critical importance of data completeness for developing robust, transferable eruption forecasting systems.
How to cite: Martanto, M., Caudron, C., Lecocq, T., Syahbana, D. K., and Nugraha, A. D.: Eruption Forecasting Using Random Forest on Single-Component Seismic Data: Insights from Three Indonesian Volcanoes (Semeru, Lewotobi Laki-laki, and Ruang), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16967, https://doi.org/10.5194/egusphere-egu26-16967, 2026.
Monitoring volcanic unrest at complex volcanoes such as Mt. Etna remains challenging due to the coexistence of diverse seismic sources, including volcano-tectonic (VT) earthquakes, sustained tremor and strong scattering in heterogeneous structures. Traditionally, such processes are investigated using translational seismometers alone, potentially limiting the characterization of the underlying wavefield and its physical interpretation.
In this study, we explore the added value of combining translational, rotational, and distributed dynamic strain sensing (DDSS) observations to investigate seismic activity during the December 2025/ January 2026 eruptive activity of Mt. Etna. We analyze six-component ground-motion recordings from a rotational sensor co-located with a conventional seismometer, complemented by DDSS measurements along a nearby fiber-optic cable. Using root-mean-square (RMS) amplitude analyses we examine the temporal evolution of seismic energy associated with tremor and VT activity across the different sensing modalities.
Preliminary results indicate that rotational and translational measurements capture complementary aspects of the volcanic wavefield, with rotational data emphasizing continuous, wavefield-dominated energy components, while translational recordings highlight both impulsive and sustained signals. DDSS observations provide dense spatial sampling, offering additional constraints on signal coherence, propagation characteristics, and source localization. When analyzed jointly, these datasets reveal a more coherent and interpretable picture of volcanic unrest than any single sensor type alone.
Our observations suggest that multi-sensor seismic monitoring, integrating translational, rotational, and DDSS measurements, is particularly advantageous in complex volcanic environments where scattering, anisotropy, and mixed source processes complicate traditional analyses. This work highlights the potential of such integrated approaches for improving the detection, characterization, and interpretation of volcanic seismicity and motivates their broader application in future volcano monitoring strategies.
How to cite: Izgi, G., Currenti, G., Eibl, E. P. S., Vollmer, D., Pellegrino, D., Pulvirenti, M., Alparone, S., Larocca, G., and Jousset, P.: More Than Shaking: What Rotations and Strain Reveal About Volcanic Unrest at Mt. Etna, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10412, https://doi.org/10.5194/egusphere-egu26-10412, 2026.
This study consists of one branch of an ongoing push to understand, locate, and leverage distributed local events on volcanoes with the dual goal of segmenting volcanic and non-volcanic activity and directly imaging the shallow volcanic edifice. Typically, locating small events on volcanoes is particularly difficult due to their emergent appearance and lack of discernable ballistic waves, precluding any metrics related to travel time. Furthermore, edifice imaging through passive approaches is generally limited due to a lack of stable frequency information above ~1 Hz, truncating surface wave sensitivity to mid-crustal scales. Here, we show a two-pronged approach to tackling these problems: 1) The scattering structure of the volcano is studied in detail using active sources and lava lake eruptions coupled with Monte Carlo Radiative Transfer simulations, permitting a full understanding of seismogram envelopes for a given source location. 2) Coda correlations of distributed icequakes and eruptions have been shown to yield very high-quality Green’s functions at frequencies up to 10 Hz. Beyond cutting scatter-based imaging, these can be used to greatly extend the frequency range of dispersion curves, and thus yield valuable upper edifice information that can be coupled with matrix-based scattering imaging effort.
How to cite: Chaput, J., Galvan, I., Reisinger, R., Aster, R., and Grapenthin, R.: Towards detecting, classifying, locating and leveraging distributed events in strongly scattering media, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22899, https://doi.org/10.5194/egusphere-egu26-22899, 2026.
Understanding geodynamic processes between Tenerife and Gran Canaria is essential for assessing seismic and volcanic hazards in the Canary Islands. The GUANCHE project characterizes seismicity, subsurface structure, and related phenomena through an integrated approach, combining land-based and ocean-bottom seismic networks.
The land-based campaign ran from April 2023 to December 2024, with 13 temporary stations across Gran Canaria transmitting real-time data to the IGN analysis center. Three high-quality sites were upgraded to permanent IGN stations after the campaign, ensuring continued seismic monitoring of the area. The marine component, using ocean-bottom seismometers (OBS), was deployed in January 2024, with data collected in June 2024. Observations from these temporary networks were integrated with the existing permanent network in Tenerife and Gran Canaria to provide a comprehensive dataset for seismic investigations.
This integrated network improves detection and localization of low-magnitude seismic events. A 3D velocity model derived from project data was applied to refine earthquake locations, providing the basis for clustering, which reveals distinct seismogenic zones and a complex pattern of activity at multiple depths. Focal mechanisms were determined for the largest earthquakes (Mw > 3.5) using TMS inversion, offering additional constraints on active faulting and regional stress.
These results highlight the value of integrated seismic monitoring for understanding seismicity patterns and geodynamic processes. This study is a collaborative effort between the Instituto Geográfico Nacional (IGN) and the Instituto de Ciencias del Mar (ICM), combining expertise in seismic monitoring and marine seismici
How to cite: Domínguez Cerdeña, I. F., Villaseñor, A., del Fresno, C., Bartolomé, R., Suárez, E. D., Barco, J., Alonso, E., Pérez-Frías, F. M., Martínez, I., Carrasco, J. M., Gómez-Liste, B., Rechcigyer, V. P., Manzanedo, M. V., Pereda de Pablo, J., and Martín Silván, A.: Integrated Seismic Monitoring of Tenerife and Gran Canaria: Insights from OBS and Land-Based Networks, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13331, https://doi.org/10.5194/egusphere-egu26-13331, 2026.
In 2021, an eruption began in the Geldingadalir valley in southwest Iceland, lasting six months. This eruption exhibited a constantly changing eruption dynamic recorded as volcanic tremor of varying duration and amplitude. In May 2021 a transition occurred, from continuous tremor in the early phase of the eruption, to minute-long tremor episodes. Throughout this period the vent featured an active lava lake. On 2 July, the lava lake drained and several ash-rich plumes rose from the crater between 3:00 and 5:00 am. The plumes were accompanied by several transient seismic and acoustic signals. Following these events, the volcanic tremor shifted from minute-long to hour-long episodes.
Here, we use a multidisciplinary approach combining video footage with seismic and acoustic data to investigate the source process and its potential link to the observed tremor transition. We performed a source inversion of the seismically strongest event using seismometers within 6-8 km distance from the active crater. We tested different source models and compared the simulated waveforms to those that were observed to constrain the source. In addition, we calculated the Volcanic Acoustic–Seismic Ratio (VASR) using seismic and acoustic tremor recordings. The VASR reveals a decrease over time. The local webcam footage provides an insight into surface processes including inner crater collapses preceding several ash-rich plumes. This observation suggests a potential link between shallow collapses, plume generation and seismic and acoustic signals. These collapses may have modified the shallow conduit and caused the transition from minute-long to hour-long episodes.
How to cite: Joachim, A., Heimann, S., Lamb, O. D., Eibl, E. P. S., Barnie, T., Gudnason, E. Á., Ágústsdóttir, T., Thordason, T., Hersir, G. P., Winder, T., Rawlinson, N., Fischer, T., Doubravová, J., and Burjánek, J.: Seismic, acoustic, and visual observations of ash-rich plume events during the Geldingadalir eruption, Iceland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10750, https://doi.org/10.5194/egusphere-egu26-10750, 2026.
Unrest has been ongoing on the Reykjanes Peninsula, Iceland, since 2019, with inflation in the Fagradalsfjall and Eldvörp-Svartsengi volcanic centres resulting in a series of volcanic eruptions beginning in 2021. We have operated a permanent broadband seismometer network on the peninsula since June 2020, complemented by networks run by several other groups. Recently, these were supplemented by 24 three-component nodes for two months starting in September 2025, which provided improved coverage in the western part of the peninsula, and further enhanced both the spatial footprint and density of the combined arrays.
Using this new dataset, and taking advantage of a period of relative volcanic and seismic quiescence, a new 3D shear wave velocity model for the peninsula is constructed from inter-station surface wave dispersion curves extracted from ambient seismic noise cross-correlations. The dense node deployment also allows analysis of shallow crustal anisotropy, thus helping to pinpoint magmatic storage regions and areas of shallow fractures. The final model spans the shallow crust from the surface to 8 km depth, with lateral model resolution approaching 1 km above the brittle-ductile transition. This allows imaging of the Reykjanes, Fagradalsfjall and Eldvörp-Svartsengi volcanic systems, as well as of geothermal fields on the peninsula.
How to cite: Pizii, W., Rawlinson, N., Winder, T., White, R. S., Brandsdóttir, B., Ágústsdóttir, T., Doubravová, J., and Burjánek, J.: New images of volcanic systems on the Reykjanes Peninsula, Iceland, from ambient noise tomography using a regional node array , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11833, https://doi.org/10.5194/egusphere-egu26-11833, 2026.
Piton de la Fournaise volcano on La Réunion island is a shield volcano that showed annual eruptive behavior since 2014. Following the last eruption of this eruptive cycle in 2023, only seismic crises were detected, but no eruption occurred until the time of writing, making the analysis of the 2023 eruption especially important. The 2023 eruption of Piton de la Fournaise volcano began on 2 July with two fissure openings on the northeastern flank, followed by a third eruptive vent on the southeastern flank that lasted until 10 August. We analyze data from a temporary seismic array on the western flank within Enclos Fouqué Caldera and the permanent network from the Volcanological Observatory of Piton de la Fournaise (OVPF-IPGP) to investigate the eruption dynamics.
The tremor frequency range varies slightly between the three fissure activity periods but is mostly concentrated between 0.8 and 4 Hz. Tremor amplitude and GNSS measurements at the summit crater show similar changes for the start and towards the end of the eruption as previously observed at the volcano. While the network analysis provides highly accurate locations for the three distinct fissures, we only obtain well fitting back azimuths (BAz) for specific times from the seismic array. Slowness results from the array however help distinguish the tremor signal into surface and body waves, and for certain phases even indicate the existence of two distinct tremor sources.
The deviating array back azimuths that are observed for the surface waves are interpreted to be related to the medium heterogeneity within the crater region including topographic effects. Our preliminary results, combining two different methods allow the determination of two tremor signals for one fissure site that exhibit different frequency ranges and amplitudes and possibly originate from both subsurface and surface sources. We assume that surface activity is dominating the analysis, but once decreased, a weaker tremor signal at depths becomes visible.
How to cite: Ohrnberger, M., Vesely, N. I. K., Eibl, E. P. S., Journeau, C., Duputel, Z., Vollmer, D., Brunet, C., Lauret, F., and Ferrazzini, V.: First insights into the 2023 Piton de la Fournaise eruption: Revealing two distinct tremor signals, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10978, https://doi.org/10.5194/egusphere-egu26-10978, 2026.
Seismic tremor is widely monitored for eruption forecasting, yet its use requires improved understanding of its source processes, which remain debated. Tremor is commonly attributed to magma transport or fluid-induced resonance within volcanic plumbing systems. However, alternative studies suggest that fluids may not be required: weak, unconsolidated edifice materials geomechanically near the brittle–ductile transition can undergo diffusive brittle failure at room temperature, producing numerous low-amplitude, small-stress-drop seismic events that merge into tremor. Minor stress perturbations—caused by magma flow, gas influx, or gravitational loading—may be sufficient to trigger such dry mechanical failure.
Here, we investigate episodic high-frequency tremor (10–20 Hz) recorded at the summit of Mt. Etna during a dense seismo-acoustic deployment in summer 2022. Despite strong attenuation and scattering at these frequencies, we show that variations in the seismo-acoustic energy ratio across tremor episodes reveal differing conditions under which tremor is produced. Using multi-array beamforming and 3D grid-search techniques, we locate tremor sources in multiple regions, including both degassing-related and non-degassing areas. Synthetic tests indicate that some tremor episodes likely comprise multiple simultaneous sources, consistent with diffusive brittle failure. Frequency–magnitude analyses further support a model in which tremor arises from sequences of small-magnitude, very low stress-drop events merging into tremor due to the cumulative scaling observed and comparison with previous numerical work on seismic event population. Together, our results indicate that volcanic tremor does not necessarily require fluid movement and may also be generated by dry brittle failure processes.
How to cite: Weber, M., Bean, C., Tary, J. B., Soubestre, J., Lokmer, I., De Angelis, S., Zuccarello, L., and Smith, P.: Implications for existing tremor generation models on volcanoes through newly observed high-frequency tremor on Mt. Etna, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13585, https://doi.org/10.5194/egusphere-egu26-13585, 2026.
Continental volcanic arcs are driven by melting in the mantle wedge between a subducting oceanic plate and overriding continental plate. These melts are emplaced within the continental crust where they then fractionate and evolve, producing silicic volcanic rocks. From observations of these systems globally, we understood them to have magmatic plumbing networks organized into transcrustal systems, and while the geometries of these systems are somewhat constrained, the links between magma storage regions, melt migration and surface unrest remains poorly understood. At Laguna Del Maule (LdM) in central Chile, where volcanic unrest is being currently monitored, we use two densely deployed seismic datasets of nodal and broadband seismometers to study these connections in detail. Here, we present interpretations using well constrained earthquake locations and high resolution crustal-scale seismic imaging using Receiver Functions (RFs), to infer the magma plumbing network and interconnectivity within this modern arc volcano setting.
Over 4300 events were detected within the periods between 2015-2018 and 2022-2024 and are divided into shallow and deep groups. Shallow seismicity is separated into clusters consistent with prior observations that link fault activity to shallow magma intrusion. Those events occurring within the deep crust (~12-30 km) are a new observation, containing a mixture of high and low frequency earthquakes. Through Frequency Index Analysis, we classify those deep events with low frequencies as Deep Long Period earthquakes (DLP). These have been observed in other volcanic arcs, but this data contains the first evidence of DLP seismicity within the Andes. The deep higher frequency events are provided in a pronounced one-day swarm of activity in 2018, all with similar magnitude and frequency index. The swarm has a vertical extent between ~21-26 km depth, and we interpret this activity to be a Volcano-Tectonic swarm (VT) related to magma migration within the middle-lower crust. In the RF images, the VT swarm is located between the top of a low velocity zone (LVZ) in the lower crust, and the base of an upper crust LVZ. The lower crust LVZ likely represents an area of deep magma storage that intermittently incubates the upper crust system with batches of basic magmas. RF images of the upper crust LVZ are consistent with prior geophysical estimates of the geometry and approximate spatial extent of LdMs shallow magma chamber.
Three months following the deep VT swarm, vertical surface uplift in the local GPS record accelerates. We therefore infer that the VT swarm was driven by the delivery of a new batch of magma from lower to upper crustal magma reservoirs. This applied additional pressure to the base of the upper crustal reservoir, leading to a surficial response in a lag-time consistent with the systems hydraulic diffusivity (~20 m2/s). Since this inflation rate has been maintained at least until 2020, the VT swarm may represent the establishment of a new preferred magma ascent path. These results indicate that volcanic unrest is preceded months in advance by seismic activity occurring within the middle-lower crust, applying bottom-up reservoir pressurization in arc volcanoes.
How to cite: Bradford, J., Mahanti, S., Kiser, E., Beck, S., Fernandez, M., Porter, R., Maharaj, A., Howe, H., Ortiz, G., and Saez, M.: Magma Migration at Laguna Del Maule, Chile, Using Well Constrained Seismicity and Receiver Function Imaging, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15346, https://doi.org/10.5194/egusphere-egu26-15346, 2026.
The Eifel region (southwest Germany) is an intracontinental volcanic field of distributed explosive centers, with the last major eruption occurring at the actively degassing Laacher See volcano in 13ka. The temporary Eifel large-N seismic network was deployed here between September 2022 and August 2023, which significantly increased station coverage allowing for a detailed study of the subsurface magmatic system. We use local earthquakes to study the attenuation properties of the subsurface structure, targeting Laacher See volcano and its surroundings.
Starting with an automatically derived earthquake catalog, we first perform a number of quality checks to ensure we only use the cleanest waveform traces and picks. Then, we estimate scattering from peak-delay measurements, i.e. the delay of the maximum energy after the S-wave. Our preliminary findings suggest the presence of two upper crustal structures beneath Laacher See, outlined by areas of high scattering, which are typically associated with the presence of small-scale heterogeneities or mechanical discontinuities (e.g. fractures, faults) and range from the surface to 8 and 13 km below sea level. Their proximity to Laacher See suggests that the rise of fluids may be facilitated by these structures. Further analysis will have to show whether the data can also be used to quantify absorption, which would shed even more light on fluid pathways.
How to cite: Bramwell, L., Reiss, M., and De Siena, L.: Preliminary imaging of the Eifel Volcanic Field from seismic scattering , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18644, https://doi.org/10.5194/egusphere-egu26-18644, 2026.
The Tatun Volcano Group (TVG), adjacent to the densely populated Taipei metropolitan region in northern Taiwan, is an active volcanic system where a large number of earthquakes have been observed. Although the previous studies have reported that volcanic fluids exist beneath the surface, how these fluids change over time and influence local earthquakes has remained unclear. In this study, we examined more than 12,000 earthquakes recorded between 2014 and 2021 to explore how the behavior of earthquakes and the physical properties of the seismogenic zone vary with time. By analyzing patterns in frequency-magnitude distribution of earthquakes and seismic wave velocities within the seismogenic zone, we found that the triggering mechanisms for earthquakes in the TVG shift over time, possibly due to the varying influence of volcanic gases, hydrothermal waters, and stress. This study deciphers the dynamic nature of the TVG and improves our understanding of the volcanic risk near the Taipei metropolis.
How to cite: Pu, H.-C., Lin, C.-H., Lai, Y.-C., and Shih, M.-H.: Temporal Variations in Earthquake Triggering Mechanisms in the Tatun Volcano Group, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2705, https://doi.org/10.5194/egusphere-egu26-2705, 2026.
Strokkur geyser in the Haukadalir valley in south Iceland is an erupting hot spring that allows studying hydrothermal processes. Since March 2020, we have continuously monitored Strokkur using three seismometers located ~40 m from the conduit. This long-term dataset has enabled the creation of a high‑resolution catalogue containing more than 760,000 individual water‑fountain events, which has previously been used to investigate eruption types, driving mechanisms, and the influence of air temperature and wind on geyser dynamics.
In this contribution, we present a striking change in Strokkur’s behaviour that occurred on 18 October 2024 at 18:00. Following this moment, the geyser began producing a larger number of water fountains per eruption, more water fountains per hour and exhibited a markedly shorter recharge cycle. Simultaneously, several neighbouring hot springs activated or increased their activity. Because the onset of this transition was captured seismically, the dataset offers a rare opportunity to examine the triggering mechanism and its implications for subsurface fluid pathways.
By analysing the spatio‑temporal evolution of seismic signals associated with this behavioural shift, we explore the underlying processes driving the system’s reorganisation. The study highlights the value of dense seismic monitoring and detailed event catalogues for understanding hydrothermal dynamics, and it provides insights into geothermal systems and their time‑dependent changes.
How to cite: Eibl, E. P. S., Izgi, G., Walter, T. R., Heimann, S., Hersir, G. P., Guðnason, K. J., and Kristjánsson, V.: A high‑resolution water fountain catalogue reveals an abrupt hydrothermal change at Strokkur geyser, Iceland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10564, https://doi.org/10.5194/egusphere-egu26-10564, 2026.
Regularly pulsating emissions are frequent during volcanic activity, especially at open vent mafic systems. Most typical of such emissions is puffing, i.e., the intermittent or periodic emission of pressurized gas volumes from a vent, with or without the ejection of pyroclasts. Puffing is usually interpreted as the result of the explosion of gas bubbles at the surface of a static magma column. Here, we experimentally demonstrate that a steady gas flux can be transformed into a pulsating flux by closed pipe resonance, and provide field evidence for this process occurring at Mt. Etna volcano (Italy) in 2023. In laboratory, we inject pressurized air through a valve system and into a pipe of variable length and 4 cm in diameter. At certain inlet pressures, pipe resonance is triggered and the air flow from the pipe opening (nozzle), visualized by the injection of fog, pulsates. In particular, high-speed imaging at the nozzle revealed the repeated formation of vortex rings alternating with air re-entering the pipe nozzle in a kind of ‘backwash’. Video analysis reveals that air fluctuations at the nozzle have characteristic resonance frequencies that agree with the closed-pipe resonant frequency of the pipe. The same frequencies appear in the power spectrum of the acoustic signal from the experiment, supporting the notion that standing pressure waves in the pipe control the temporal flux of outgoing air flow. Puffing activity at Etna in 2023 produced volcanic vortex rings (VVR) alternating with ‘backwash’ phases. Thermal video imagery displays two characteristic frequencies of temperature changes above the vent, at 0.25 and 0.5 Hz, with a possible third one at 0.75 Hz, in agreement with a resonance process. No peak appears at these frequencies in the spectrum of the infrasonic signal associated with puffing. We conclude that puffing activity and VVR emission at Etna was controlled by conduit resonance that modulated the flux from a steady source of volcanic gases. As far as we can tell from the volcanology literature, despite organ-pipe resonance invoked to explain seismic harmonic tremor and acoustic signals, this the first time that conduit resonance is observed to control volcanic emissions. Resonance modulation may potentially extend to other pressure-controlled volcanic processes, such as bubble explosion, fumarolic activity or control the unsteady flux of erupted material during sustained and larger explosive eruptions, thus representing a key factor to be considered in future investigations.
How to cite: Spina, L., Taddeucci, J., Iezzi, F., Biensan, C., Penacchia, F., Weber, M., Zuccarello, L., De Angelis, S., Palladino, D., and Scarlato, P.: Conduit resonance modulation of volcanic puffing (and maybe more), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17156, https://doi.org/10.5194/egusphere-egu26-17156, 2026.
In 2010, the station IS42 was the first infrasound station to be installed in the Azores, located on Graciosa Island in the central group of the Azores archipelago, in the middle of the North Atlantic. This station integrates the International Monitoring System (IMS) of the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO). Although the mission of the CTBTO is to put an end to nuclear tests, the long-term infrasound data recorded by IMS have proven to be very valuable for monitoring and understanding natural phenomena, including seismo-volcanic activity in the Azores.
With the aim of monitoring the 2022 seismo-volcanic crisis on São Jorge Island, a first portable infrasound array was deployed to complement the data recorded from the permanent IMS station and enrich the archipelago’s monitoring network. A second portable array was subsequently deployed on Terceira Island, and an additional array is planned for deployment on Faial Island later this year, further strengthening the Azores infrasound monitoring network.
This study analyses the performance and behaviour of the portable arrays, using IS42 as a reference station. We applied a multi-channel correlation analysis in the time domain to evaluate the influence of background noise on the recorded signals and assess the impact of station location and environmental conditions on the detections. Root-mean-square (RMS) noise analyses were combined with source direction estimates based on the detections’ back azimuths. Seasonal analyses of the detections revealed a strong influence of atmospheric conditions on noise levels and, consequently, on back azimuth directions. These results highlight the importance of noise characterisation of integrated infrasound observations in oceanic islands.
How to cite: Silva, L. I., Matos, S., Marchetti, E., and Wallenstein, N.: Azores Infrasound Network: Analysis of background noise, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13765, https://doi.org/10.5194/egusphere-egu26-13765, 2026.
Infrasound has been widely applied to the remote monitoring of explosive volcanic eruptions. Although no active volcanoes are currently present within South Korea, explosive activity in neighboring regions can still generate transboundary hazards that require effective remote monitoring. In this context, we present a quantitative assessment of volcanic eruption detectability using the Korea Infrasound Network (KIN).
The KIN has been operated for more than two decades and was originally established to monitor local and regional acoustic sources and to discriminate between natural and anthropogenic signals. The network consists of Chaparral M2 infrasound sensors, each of which has a flat response from 0.1 to 200 Hz. Since 2011, eight infrasound arrays with apertures ranging from 0.15 to 1.68 km have been fully operational. We evaluate the detectability of eruptions with VEI ≥ 3 that have occurred since 2011, examining detection characteristics as a function of distance, azimuth, and atmospheric propagation conditions. Detection was performed using the Progressive Multi-Channel Correlation (PMCC) algorithm to identify coherent infrasound signals.
Many eruption signals recorded by the KIN extend into frequencies below the nominal flat-response bandwidth and are often obscured by persistent microbarom noise. Despite these limitations, volcanic eruptions were conditionally detected depending on eruption size and atmospheric propagation conditions. The analyzed cases include the 2022 Hunga Tonga–Hunga Haʻapai eruption (VEI 5), the 2020 Taal and 2021 Fukutoku-Oka-no-Ba eruptions (VEI 4), and several VEI 3 eruptions such as Asosan, Kirishimayama, and Raikoke.
Our results indicate that automated eruption detection using KIN is feasible, particularly at the TJIAR array in central South Korea. A long-term PMCC detection catalog spanning approximately 15 years (since 2011) was compiled for TJIAR and compared with independent eruption records from the Tokyo Volcano Ash Advisory Center and the Global Volcanism Program to assess detection reliability. This study represents the first long-term assessment of volcanic infrasound detectability based on the KIN. In addition, low-frequency infrasound sensors (MB3d) with an extended dynamic range were collocated at one of the KIN arrays in 2025 to improve low-frequency detectability. Ongoing work focuses on assessing improvements in eruption detectability through comparisons between legacy and upgraded sensor configurations, with implications for the development of an infrasound-based automated eruption detection and long-term monitoring of explosive volcanic eruptions in East Asia.
How to cite: Park, I. and Che, I.-Y.: Quantitative Assessment of Remote Volcanic Eruption Detectability Using the Korea Infrasound Network, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8960, https://doi.org/10.5194/egusphere-egu26-8960, 2026.
