This session will bring together experts to present the latest innovations in seismic attenuation research. We welcome theoretical and applied contributions, from work deepening fundamental understanding to studies showcasing practical applications.
Topics of interest include:
• Theoretical advancements that improve understanding of attenuation processes, including scattering and intrinsic absorption.
• Resolve Earth’s internal structure through analysis of attenuation data.
• Numerical simulations of the relevant equations for seismic wave propagation in heterogeneous media and attenuation.
• Applications to the study and characterization of seismic sources.
• Attenuation studies in seismic hazard and damage assessment, including ground motion models and the effects of shaking on structures and infrastructure.
• Energy dispersion from geological heterogeneities, such as faults, fractures, and variations in rock properties.
• Attenuation as an indicator of energy conversion into heat, with applications to geothermal exploration and volcanic hazard assessment.
• Tomographic imaging that integrates attenuation, scattering, and absorption to investigate Earth’s structure from crust to core.
• Planetary science investigations that use seismic attenuation to probe the internal structure and dynamics of other planetary bodies.
Orals: Thu, 7 May, 16:15–18:00 | Room -2.31
Seismic anisotropy and attenuation, often quantified by the inverse of the quality factor (), are powerful, but often underexploited, indicators of fracture architecture, fluid content, and small-scale heterogeneity in the subsurface. At the same time, machine-learning (ML) methods offer flexible, data-driven mappings between seismic attributes and subsurface properties yet are not often designed to exploit seismic anisotropy and attenuation. In this contribution, an integrated workflow that combines laboratory measurements, borehole and VSP data, and surface seismic attributes with ML modelling to achieve advanced subsurface characterization in fractured carbonate systems.
Seismic waveforms collected in Abu Dhabi in the United Arab Emirates (UAE), were recorded at wide frequency range from Hertz to MHz, in the field and laboratory. The lithology of Abu Dhabi subsurface is dominated by carbonates, which are known by their high heterogeneity and multiple fracturing systems. To address the complexity caused by lithology, new methods and processing workflows have been developed and applied on the data. This includes new methods for calculating seismic attenuation from surface seismic, vertical seismic profiling (VSP), and sonic data, allowing an estimate of attenuation magnitude and its anisotropy, in addition to separating between scattering and intrinsic attenuation.
The study includes a suite of field and laboratory studies that quantify azimuthal P-wave attenuation, separate intrinsic and scattering contributions, and relate these to fracture systems and tar-mat occurrence in Abu Dhabi carbonate subsurface. These include multi-offset azimuthal VSP analyses that recover fracture strike and discriminate between open and cemented fractures using attenuation anisotropy, detailed attenuation-mode separation from VSP and sonic data, AVAz-based fracture characterization from 3D surface seismic, and ultrasonic measurements that document the sensitivity of to petrophysical properties and saturation in carbonate core plugs. Building on this physical understanding, we extend recent work on ML-based prediction of Thomsen’s parameters from synthetic and VSP data to explicitly incorporate multi-scale attenuation attributes. Training data is generated by finite-difference modeling in anisotropic, fractured carbonate media constrained by well logs, FMI, and core information from an offshore Abu Dhabi oilfield. Input features include azimuthally dependent amplitudes of direct and reflected waves, frequency- and traveltime–derived attributes. We benchmark several ML regressors (support vector regression, extreme gradient boosting, multilayer perceptrons, and 1D convolutional neural networks) and use explainable AI tools to rank the relative importance of attenuation- versus kinematics-based features.
This study demonstrates that jointly exploiting anisotropy, attenuation, and ML substantially improves the interpretability and resolution of fracture and fluid systems in complex carbonate media. The proposed workflow is generic and can be transferred to other fractured and heterogeneous settings, offering a practical route to physics-aware, data-driven seismic characterization for reservoir development and monitoring.
How to cite: Bouchaala, F., Matsushima, J., and Zhao, G.: Integrating Seismic Anisotropy, Attenuation, and Machine Learning for Advanced Subsurface Characterization, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2933, https://doi.org/10.5194/egusphere-egu26-2933, 2026.
Anelasticity is an intrinsic property of Earth’s interior and it is closely associated with temperature, partial melt, and water content. To date, the development of seismic attenuation models has lagged behind that of velocity models, due to the difficulty in distinguishing attenuation effects from velocity heterogeneities in waveforms, as well as inconsistencies across inversion methods and their resulting attenuation structures. To address these challenges, we recently developed a novel anelastic scattering-integral-based full waveform inversion (FWI) method. Its effectiveness has been verified through numerical experiments using the Northwestern United States region as a realistic case study. Specially, the method can accurately solve 3D anelastic wave equation even in the presence of strong attenuation and computes full anelastic sensitivity kernels incorporating both effects of physical dispersion and dissipation. As an application, we utilize abundant seismic waveform data from the China National Seismic Network to establish, for the first time, a high-resolution 3D anelastic structure model of the lithosphere and asthenosphere in the eastern Tibetan Plateau. Waveform comparisons and checkerboard tests verify the reliability of the inverted model, which achieves a maximum horizontal resolution of 0.6°×0.6°and a maximum vertical resolution of 25 km. This highly accurate anelastic model provides important structural constraints for understanding the deep processes of material extrusion at the eastern margin of the Tibetan Plateau.
This work is supported by the National Natural Science Foundation of China (42204056).
How to cite: Wang, N.: 3D anelastic full waveform inversion and its application, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4131, https://doi.org/10.5194/egusphere-egu26-4131, 2026.
Attenuation is a fundamental process of seismic wave propagation, yet its role in site–city
interaction remains poorly constrained and rarely quantified. In particular, un- derstanding
how buildings collectively dissipate seismic energy through scattering and absorption is essential
for assessing earthquake impact in urban areas. Numerical studies have recently introduced the
concepts of urban attenuation and urban mean free path to describe these processes. However,
observational evidence based on real data is still lack- ing, leaving open questions about how
such mechanisms manifest in practice.
In this study, we address this gap using the META-FORET experiment, in which a dense
pine forest is considered as a natural analogue of an urban environment. Trees act as distributed
reso- nant scatterers, allowing us to investigate urban-like scattering and attenuation processes
under well-characterized and repeatable conditions. We analyze both ambient noise and active
shot data to extract key ground motion parameters that are directly relevant to seismic hazard
assessment, including horizontal-to-vertical spectral ratios (H/V), spatial variability of ground
motion, wave attenuation and intensity indices. Passive data reveal frequency-dependent
scattering signatures around tree resonances (20 and 50 Hz), includ- ing perturbations of H/V
curves, reduced coherence and absorption.
Active shot analyses further show a systematic reduction of Arias intensity and a strong
increase in Trifunac duration within the forest compared to the open field, especially near
resonance frequencies. These observations indicate that resonant scatterers redistribute seismic
energy, reducing direct-wave amplitudes while enhancing coda wave durations.
This study provides the first experimental quantification of urban-like scattering and
attenuation from real seismic data. By bridging fundamental wave physics and ground motion
indicators, we propose a noise-based technique to characterize seismic wave atten- uation in
urban environments.
Keywords: urban-like scattering, wavefield coherence, absorption, seismic attenuation,
spectral ratios.
How to cite: Celorio Murillo, M. H., Guéguen, P., Touma, R., and Roux, P.: Experimental characterization of urban-like scattering and attenuation from a dense nodal array: implications for seismic ground motion, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14980, https://doi.org/10.5194/egusphere-egu26-14980, 2026.
Cratons are traditionally considered to be long-lived and stable owing to their great thickness and rigid lithospheric roots. However, increasing evidence suggests that some cratons have experienced significant lithospheric thinning and destruction. The Sichuan basin, a cratonic basin within the Yangtze Craton, is widely regarded as the cratonic nucleus owing to its long-term tectonic stability and continuous sedimentary subsidence. However, the oldest Archean basement of the Yangtze Craton, represented by the Kongling Complex, is mainly exposed in the eastern Sichuan Basin, raising the question of the spatial location of the ancient nucleus for the Yangtze Craton. Since the Mesozoic, the Yangtze Craton has been affected by the combined influences of Paleo-Pacific subduction and Cenozoic eastward extrusion of the Tibetan Plateau, and the preservation and spatial distribution of its deep lithospheric root remain poorly constrained by geophysical observations. Here, we constructed a high-resolution crustal-upper mantle attenuation model using regional Pn and Lg phases to constrain the coupling/decoupling characteristics between crust and upper mantle beneath the Yangtze Craton. The weak crustal Lg attenuation in the Sichuan Basin does not correspond to the weak Pn attenuation in the upper mantle, indicating that the lithospheric root may mechanically migrate to the eastern Sichuan Basin. The phenomenon is likely associated with the Cenozoic eastward extrusion of the Tibetan Plateau, yet the eastern Yangtze Craton appears to have undergone overall lithospheric thinning and destruction related to Mesozoic Paleo-Pacific subduction. This study was supported by the National Natural Science Foundation of China (42474084) and Deep Earth Probe and Mineral Resources Exploration-National Science and Technology Major Project (2025ZD1005302).
How to cite: Shen, L., Zhao, L.-F., Chang, X., Xie, X.-B., and Yao, Z.-X.: Crustal Lg and upper mantle Pn attenuation structure beneath the Yangtze craton and its implications for the ancient cratonic nucleus, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4670, https://doi.org/10.5194/egusphere-egu26-4670, 2026.
Within the collision zone between the Arabian and Eurasian plates, the Anatolian Plateau represents an early stage in the closure of the Neo-Tethys Ocean (Teknik et al., 2025). The uplift mechanism of the Anatolian Plateau remains debated, as the primary geodynamic drivers likely vary regionally. While upper-crustal shortening dominates the northern margin of Central Anatolia, slab break-off and mantle upwelling are key along the southern and interior margins (Şengör et al., 2008; Yildirim et al., 2011). These processes are not isolated but may be geodynamically linked through subsequent shifts in plate motion and mantle flow following slab break-off. The Pn wave is a seismic phase that propagates primarily within the uppermost mantle. Its attenuation characteristics serve as a proxy for physical properties such as temperature, pressure, and water content in this region. Therefore, high-resolution attenuation tomography of the uppermost mantle using Pn waves can provide key constraints on the tectonic evolution of the Anatolian Plateau.
In this study, we collected 23,830 seismic waveform data from 853 events recorded by 717 seismic stations between July 1996 and August 2025. Using a joint inversion method (Zhao et al., 2015), we constructed a broadband (0.05 - 20.0 Hz) high-resolution (1.0 1.0) Pn-wave attenuation model for the Anatolian Plateau. A prominent high-Q region observed in the southwestern part of the study area represents the Aegean Slab while a localized high-Q zone surrounded by low-Q anomalies (at approximately 36°E, 39°N) correlates with volcanism in the Central Anatolian Plateau. This work was supported by the National Natural Science Foundation of China (No. 42430306).
How to cite: Cheng, Q.-Y., Zhao, L.-F., Eken, T., Xie, X.-B., Li, H.-Y., and Yao, Z.-X.: Pn-wave attenuation tomography in Anatolia and its implications for slab break-off, mantle upwelling, and plateau uplift, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5341, https://doi.org/10.5194/egusphere-egu26-5341, 2026.
Seismic attenuation provides key constraints on the thermo-mechanical state and small-scale heterogeneity of the crust, but high-frequency observations are strongly affected by the coupling between intrinsic attenuation (Qi) and scattering attenuation (Qsc). This coupling hampers conventional attenuation inversions, particularly in tectonically complex regions such as the eastern margin of the Tibetan Plateau. High-frequency seismic coda wave envelopes provide critical insights into the influence of attenuation structures on energy evolution and serve as an essential data source for scattering studies. In this study, we combine unsupervised machine learning and physics-based envelope modeling to investigate crustal intrinsic and scattering attenuation across the Longmenshan Fault Zone and adjacent regions. We first apply a Conditional Variational Autoencoder (CVAE) to tens of thousands of high-frequency (2–4 Hz) P- and S-wave envelopes, including their coda, recorded by a regional seismic array. By conditioning on source–receiver distance, the CVAE suppresses geometric effects and extracts latent variables that characterize lateral and vertical variations in envelope shape. Two latent variables are sufficient to describe the dominant envelope features: the first is primarily associated with variations in P-to-S energy ratios and correlates with intrinsic attenuation, while the second reflects changes in envelope width and peak timing, consistent with scattering strength. The spatial distribution of the intrinsic-attenuation-related latent variable reveals a clear contrast between the Tibetan Plateau and the Sichuan Basin, whereas scattering-related variations are mainly controlled by local small-scale heterogeneity and show no systematic dependence on large-scale tectonic units. Guided by these results, we further perform three-dimensional high-frequency envelope modeling using radiative transport theory on ~61,000 three-component seismograms. We constructed two-layer models of intrinsic attenuation and small-scale scattering structures for the crust of Sichuan Basin and Tibetan Plateau regions, respectively. The sedimentary layer of the Sichuan Basin displays strong scattering and intrinsic attenuation, suggesting a porous, potentially fluid-rich structure, which aligns with the presence of abundant oil and gas resources. The relatively weak scattering and intrinsic attenuation in the Sichuan Basin's crust indicate its nature as an ancient, stable geological block. The lower crust of the Tibetan Plateau shows stronger intrinsic attenuation than the upper crust but significantly weaker scattering, suggesting the presence of a high-temperature, viscous flow structure in the region. The upper crust of the Tibetan Plateau exhibits significantly stronger scattering and intrinsic attenuation compared to that of the Sichuan Basin, reflecting the extensively faulted and fractured structure due to ongoing tectonic collisions.
How to cite: Zhang, B., Li, J., Ni, S., and Zhang, H.: Crustal Scattering and Intrinsic Attenuation Across the Eastern Margin of the Tibetan Plateau Revealed by High-Frequency Coda Waves, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6112, https://doi.org/10.5194/egusphere-egu26-6112, 2026.
Hong Kong, one of the most densely populated financial centers in the world, has received limited attention in subsurface structure imaging due to its tectonic quiescence. However, it sits atop the core of the Lianhuashan Fault Zone and was a center of multiple super volcanic eruptions during Yanshanian movement. The complex fault systems and widespread geothermal resources in adjacent region are legacies of these intense tectonic events. We deployed a temporary array of 13 portable seismic nodal sensors covering Hong Kong core area and recorded 21-day seismic data. Using ambient noise adjoint tomography, we imaged the upper 8 km of the crust at high resolution. Significant fault-controlled heterogeneity revealed indicates both geothermal potential and seismic hazard. A deep-seated fault beneath Lantau Island experienced intense fault dilation and volcanic activity as it served as a main magma conduit during Mesozoic. It left behind fractured felsic rocks (low velocity) and rigid mafic intrusions (high velocity), forming a potential seismogenic structure. Pronounced low-velocity anomaly beneath Tai Mo Shan may reflect geothermal activity. Combined with pervasive fracturing and abundant precipitation in Hong Kong, this suggests the presence of an uplift-driven convective geothermal system in the region.
How to cite: Li, Z., Wang, X., Liu, X., Yang, H., and Zhao, G.: Ambient Noise Tomography Reveals Heterogeneous Structure of the Igneous Rocks in Hong Kong’s Upper Crust, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9760, https://doi.org/10.5194/egusphere-egu26-9760, 2026.
Seismic attenuation provides a highly sensitive constraint on fluid-driven processes in the shallow subsurface. These attenuation-derived spatiotemporal insights complement conventional seismic velocity monitoring and can be used for environmental monitoring and engineered subsurface infrastructure management. In this study, we implemented time-lapse Rayleigh-wave attenuation measurements during controlled shallow water injections to quantify the coupled evolution of seismic attenuation and pore-fluid infiltration. The monitoring experiment was conducted over a 14-day period at a localized test site where two vertical wells were hydraulically connected by a permeable pipeline. The frequency-dependent Rayleigh-wave attenuation coefficients are estimated from spectral-ratio slope fitting of multichannel active-source surface-wave records. These measurements are subsequently combined with phase velocities and S- and P-wave velocities to invert for depth-dependent energy dissipation factors and within a layered medium. The resulting attenuation variations are interpreted as proxies for changes in fluid saturation and hydrological properties in the shallow subsurface. The attenuation images clearly delineate the boundary between the pipeline and the surrounding medium and exhibit pronounced temporal variations driven by injection-induced fluid migration. Daily time-lapse variations of attenuation over the 14-day experiment reveal frequency-dependent responses to the intermittent injection schedule, with peak values near the period of maximum injection. These patterns reflect the migration and redistribution of pore fluids within the near-surface formation. The inverted Q images further identify localized low-Q zones around the pipeline and the two wells, indicating enhanced energy dissipation associated with fluid accumulation and increasing saturation. This study establishes a powerful framework for monitoring fluid migration and its physical impacts from time-lapse seismic attenuation. Our results highlight the importance of attenuation-based imaging for advancing high-resolution characterization of near-surface hydrological and engineered subsurface environments.
How to cite: Liu, X., Mi, B., Xia, J., Guan, J., Zhou, J., and Sun, H.: Spatiotemporal monitoring of soil moisture dynamics from Rayleigh-wave attenuation: A controlled field experiment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6591, https://doi.org/10.5194/egusphere-egu26-6591, 2026.
The conspicuous eastward expansion of the Tibetan Plateau is evident and uncontroversial from geological surface expressions and remote sensing, but the mechanisms that cause it have remained enigmatic. The extrusion has been attributed to ductile deformation of a weak crust. This is consistent with the discovery of mid-lower crustal low (seismic) velocity zones (LVZs), but the cause of crustal weakness and the origin and nature of the LVZs are debated, with competing hypotheses including channel flow from central Tibet, local fluid content, and mantle-derived processes. We present a high-resolution 3D seismic attenuation (Qp) model of the crust and uppermost mantle in southeastern Tibetan Plateau. Our results reveal high-attenuation anomalies in the middle-lower crust that overlap with previously imaged LVZs but extend across the Moho into the uppermost mantle. These anomalies correlate spatially with Cenozoic magmatism, mantle-derived helium isotope signatures, Zircon Hf-isotopes, and major strike-slip faults. This suggests that the crust in southeastern Tibetan plateau is weakened from below, possibly by upwelling induced by tearing of the subducted Indian slab.
How to cite: Zhang, H., Wang, J., Hou, Z., Xu, B., Guo, H., Thurber, C., and van der Hilst, R.: Crustal Weakening by Mantle Upwelling in Southeastern Tibetan Plateau, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17001, https://doi.org/10.5194/egusphere-egu26-17001, 2026.
Posters on site: Fri, 8 May, 08:30–10:15 | Hall X1
Seismic attenuation is important to understand the thermal and compositional state of the lithosphere, therefore sheds light on its deformation process. However, measuring the attenuation coefficient of seismic waves is still a challenging task because the phase and amplitude can be affected by both elastic velocity structures and anelastic attenuation, let alone these effects are coupled. Here, we developed a 2D joint inversion T-matrix method for the Rayleigh-wave phase velocity and attenuation coefficient simultaneously. Using a matrix inversion calculation to update the background medium Green functions with scattering series, the scattered wavefield can be fully represented in the frequency domain. First, the T-matrix method takes the coupling of elasticity and attenuation on waveform into consideration by joint inversion. Secondly, by calculating the anelastic scattering effects, 2D distribution can be obtained even for weak attenuation, which is a step towards 3D Q structure. Without time domain wave propagation simulations, the method is affordable in regional problems. Therefore, the method can be used to invert 2D Rayleigh wave phase velocity and attenuation coefficients.
How to cite: Yang, P. and Ruan, Y.: A 2D joint inversion method for Rayleigh wave phase velocity and attenuation coefficient, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1247, https://doi.org/10.5194/egusphere-egu26-1247, 2026.
Characterizing high-frequency (~10 Hz) seismic wave propagation is essential for understanding strong ground motions and improving seismic hazard assessment. High-frequency components are strongly influenced not only by source processes but also by small-scale heterogeneity along the propagation path. In the crust, vertical layering coexists with lateral heterogeneity, which plays a key role in controlling the propagation and attenuation of seismic waves. During propagation, seismic energy is reduced by intrinsic attenuation, in which energy is dissipated into heat and acoustic energy, and by scattering due to heterogeneity, which can produce apparent attenuation or amplification. In this study, we analyze S-wave coda from the 2016 Gyeongju earthquake using Multiple Lapse Time Window Analysis (MLTWA) to estimate the intrinsic (Qi), scattering (Qs), and total (Qt) quality factors in discrete frequency bands. Over the central frequency range of 1.5–22 Hz, the inferred Qs values range from approximately 398 to 4399, Qi from 185 to 1390, and Qt from 120 to 1041, revealing a pronounced frequency dependence of attenuation. The observed Qs–frequency relationship is then interpreted using a von Kármán autocorrelation model, yielding crustal heterogeneity parameters ε = 0.048, κ = 0.32, and a = 8.0 km. These parameters reproduce the empirical Qs curve and are used to generate random heterogeneous media for numerical simulations of high-frequency wave propagation. By integrating observation-based heterogenous crustal modeling, this study quantitatively constrains the influence of crustal heterogeneity on high-frequency seismic wave propagation and provides a physical basis for refining strong ground motion prediction models and improving the reliability of seismic hazard assessments.
How to cite: Lee, S., Cho, C. S., and Song, S. G.: High-Frequency Seismic Wave Simulations in Qs-Constrained von Kármán Random Media for the 2016 Gyeongju Earthquake, South Korea, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2494, https://doi.org/10.5194/egusphere-egu26-2494, 2026.
Accurate magnitude estimates and reliable propagation models are essential for seismic hazard assessment. Unfortunately, the magnitudes of small earthquakes remain subject to significant uncertainties, primarily due to complex high-frequency propagation effects. Similarly, spatial variations in attenuation properties are crucial for refining ground motion models and reducing epistemic uncertainties in seismic hazard assessment. This study proposes (1) to map attenuation properties (scattering and absorption) in Metropolitan France using the radiative transfer theory of elastic waves, and (2) to simultaneously estimate source and site spectra through a generalized inversion. The recovered source spectra provide access to the moment magnitude Mw, corner frequency fc, and apparent stress σapp.
We apply the entire inversion procedure to approximately 21,000 recordings from the EPOS-FR and CEA databases, including events with local magnitudes ML ranging from 2.0 to 5.9, and stations with hypocentral distances of less than 250 km. The estimated attenuation maps reveal strong spatial and frequency-dependent variations. Scattering dominates absorption at low frequencies (< 1 Hz), while absorption prevails at high frequencies. Strong scattering anomalies are concentrated in recent sedimentary basins at low frequencies and in deformed regions or deep sedimentary basins at medium and high frequencies. Conversely, Variscan units exhibit low scattering attenuation, especially at low frequencies. Absorption is highest in the French Alps and the western Pyrenees and lowest in the Armorican Massif. Concurrently, a catalog of 1,279 Mw magnitudes and 577 site terms is established for Metropolitan France. The obtained magnitudes are consistent with those in the unified Euro-Mediterranean catalog. Its comparison with the SI-Hex catalog highlights the importance for correcting the attenuation variations before extracting source parameters and especially the magnitude. The analysis of the apparent stress σapp reveals a moderate increase with the seismic moment M0 (scaling exponent of 0.24±0.08), without any marked regional trend. Finally, we emphasize the importance of rigorously correcting for site effects, using reference stations on bedrock and of ensuring inter-event connectivity during the generalized inversion process through the existence of common stations across event records. The next step is to integrate this approach and related results in CEA seismic alert operational framework.
How to cite: Heller, G., Sèbe, O., Margerin, L., Traversa, P., Calvet, M., and Mayor, J.: Magnitude and source spectra estimation using an elastic radiative transfer modelling of seismic wave-field attenuations: application to a French dataset. , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19330, https://doi.org/10.5194/egusphere-egu26-19330, 2026.
The existence of a typical triple junction in Colombia is crucial for understanding plate convergence and coupling among the South American Plate, the subducting Nazca Plate, and the Caribbean Plate. However, locating this triple junction is challenging due to complex geodynamic evolution and uncertainty in the slab boundaries. Here, we developed a high-resolution Lg-wave attenuation model for Colombia and surrounding areas to constrain crustal magmatic activity, link deep processes with surface volcanism, and identify potential slab boundaries. The area encompassing Central America, western Colombia, and Ecuador exhibits strong Lg attenuation and a concentration of volcanoes, indicating thermal anomalies in the crust. In line with the velocity structure, volcanism, seismicity, and isotopic dating, the thermal anomalies associated with the subducting Nazca and Caribbean slabs suggest the presence of three subducting slabs beneath the South American Plate, with a triple junction located at approximately 7.5°N, 77°W. This research was supported by the National Natural Science Foundation of China (42430306).
How to cite: Zhao, L.-F., Liu, Z., Xie, X.-B., Vargas, C. A., Tian, B., and Yao, Z.-X.: A high-resolution broadband crustal Lg attenuation model beneath Colombia and its implication for triple-junction tectonics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3654, https://doi.org/10.5194/egusphere-egu26-3654, 2026.
The Southern Granulite Terrain (SGT) in peninsular India is a high-grade metamorphic region formed by intricate Precambrian tectonic processes, serves as a natural laboratory for examining the seismic properties of solid continental lithosphere. Attenuation anisotropy shows how seismic energy loss changes with direction, giving extra information beyond just how fast seismic waves move through rock. It is particularly good at showing processes like grain-boundary relaxation, dislocation creep, and fluid assisted deformation. We have measured the shear-wave splitting parameters (, ) and attenuation anisotropy (, ) for the SKS phases recorded at 13 stations spread over the SGT using the second eigenvalue minimisation method and the instantaneous frequency matching technique, respectively. The attenuation anisotropy parameters for each station, obtained through a weighted-stacking process, vary from 0.1s to 0.85s for differential attenuation () with an average of ~0.36s and -82° to 88° for fast polarisation direction (), with the apparent fast wave () attenuating more, indicating the presence of fluid-filled fractures. Removing the attenuation effects, the station-averaged delay time () lies between 0.73s and 1.27s, with an average of ~0.99s, and fast polarisation direction () lies between -87° and 58°. We further analysed the backazimuthal dependence of the splitting parameters. The melt inclusions and the anisotropic layers beneath each station are characterised using the squirt flow model. The fractures are striking at an angle between ~49° and ~306°, and dipping at an angle between ~36° and 50°. The anisotropic layer thickness varies from 33 km to 115 km beneath the stations. Variations in attenuation anisotropy across major shear zones, like the Palghat–Cauvery and Achankovil sutures, offer important information about reactivated shear deformation, fossil lithospheric fabrics, and potential asthenospheric contributions in the SGT. This information helps to clarify the tectonothermal evolution of this ancient crustal block.
How to cite: Das, R., Hamza, F., and Saikia, U.: Probing Mantle Deformation beneath the Southern Granulite Terrain Using Seismic Attenuation Anisotropy, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4344, https://doi.org/10.5194/egusphere-egu26-4344, 2026.
Seismic attenuation offers insights into subsurface material properties, which are independent of the velocity information obtained from seismic tomography. Because seismic‐wave amplitude attenuation is sensitive to several factors such as temperature, mineral grain size, partial melt, and compositional variations, quantitative attenuation analysis provides additional constraints on the thermal and rheological state of the Earth’s interior. However, compared to seismic imaging studies, attenuation characteristics of the subsurface beneath the southern Korean Peninsula remain poorly constrained. In this study, we analyze seismic waveforms recorded at approximately 40 broadband seismic stations deployed across the southern Korean Peninsula between 2009 and 2012, and derive preliminary Rayleigh-wave attenuation estimates over the period range of 20–120 s. The results show generally low attenuation at short periods (20–30 s), which are primarily sensitive to the crust and uppermost mantle, whereas relatively high attenuation is observed at longer periods (80–120 s), corresponding to asthenospheric depths. These patterns likely reflect increasing temperature and rheological heterogeneity in the upper mantle. Future work will expand station coverage and invert the attenuation measurements to construct a detailed depth‐dependent attenuation model beneath the southern Korean Peninsula.
How to cite: Park, S. and Chang, S.-J.: Rayleigh-wave attenuation in the southern Korean Peninsula from Helmholtz tomography, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4722, https://doi.org/10.5194/egusphere-egu26-4722, 2026.
Abstract
Seismic attenuation, controlled by scattering and intrinsic absorption processes, represents a fundamental property for investigating crustal heterogeneity, fracturing, and fluid distribution. Here we present results from 3D attenuation tomography in the Calabrian Arc (Southern Italy), based on a relocated local-earthquake dataset analyzed within the MuRAT3D framework (De Siena et al. 2014). The study relies on a dedicated dataset of ~490 local earthquakes recorded between 2016 and 2024 by integrating local and national seismic networks. Event selection was designed to ensure homogeneous spatial and depth coverage while limiting clustering effects. P- and S-wave arrivals were manually picked, and earthquakes were relocated using a combined deterministic–probabilistic approach, producing a robust dataset optimized for attenuation analysis (Schweitzer, 2001; Chiappetta and La Rocca, 2024).
MuRAT3D enables a multi-parameter characterization of seismic energy loss by exploiting different portions of the seismic waveform. Scattering is investigated through Peak Delay (PD) derived from envelope broadening, while total and intrinsic attenuation are described by the quality factors Q and Qc. Analyses were carried out at discrete frequencies (1.5, 3, 6, 12, and 18 Hz), showing that only specific frequency bands yield stable and physically consistent attenuation parameters, reflecting the validity limits of the underlying assumptions and different seismic wave propagation regimes. The resulting 3D attenuation images display coherent, laterally variable patterns, with strong contrasts between continental and offshore domains and localized anomalies related to pronounced crustal heterogeneities and possible interactions with deep structures.Ongoing analyses aim to further refine attenuation patterns and their geological interpretation.
How to cite: Caporale, G., La Rocca, M., de Nardis, R., and De Siena, L.: Multi-parameter seismic attenuation tomography of the Calabrian crust (Italy) using MuRAT3D, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5110, https://doi.org/10.5194/egusphere-egu26-5110, 2026.
We estimated shear-wave splitting parameters and splitting intensity using core-refracted phases (SKS and SKKS) recorded at 90 digital broadband seismic stations across the South Indian Shield, encompassing the Western Dharwar Craton (WDC), Eastern Dharwar Craton (EDC), and Southern Granulite Terrain (SGT). Observed delay times range from 0.4 to 1.5 s, with a mean of ~0.9 s, while fast polarization directions vary from NW to NE–NNE. Although delay times show no significant variation among the three tectonic domains, fast polarization directions exhibit pronounced spatial differences. The EDC is characterized predominantly by NE–NNE orientations, the WDC by N–S to NW directions, and the SGT by a mixed pattern ranging from NW to NE. The splitting intensity varies smoothly across the region, with values ranging from 0.8 to 1.0. These observations suggest that seismic anisotropy beneath the South Indian Shield reflects a complex interplay between the Archean lithospheric architecture and subsequent domain-specific deformation driven by deep Earth processes.
How to cite: Saikia, U., Shameer, S., and Das, R.: Seismic Anisotropy and Splitting Intensity Beneath the South Indian Shield: Evidence for Archean Lithospheric Fabric and Post-Archean Deformation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6793, https://doi.org/10.5194/egusphere-egu26-6793, 2026.
Strong trade-offs between earthquake source and attenuation term remain a major challenge in source parameters inversion and attenuation structure. Spectral ratio methods alleviate this problem by using nearby small earthquakes with highly correlated waveforms as empirical Green’s functions (EGF), thereby reducing path and site effects and enabling robust relative estimation of source parameters, particularly corner frequency. However, limited signal-to-noise ratios and spikes at high frequencies significantly affect the estimation of corner frequency. In addition, different choices of EGF may further increase the uncertainty in corner frequency estimations. To reduce the effects of high-frequency spectral instability and EGF selection on spectral ratios, we first perform single-spectrum fitting to obtain physically constrained and smoothed amplitude spectra. These fitted spectra are then used to construct spectral ratios, from which corner frequencies can be robustly estimated. The source parameters constrained by the spectral ratio analysis are then incorporated as prior information, with the introduction of controlled perturbations, a joint inversion of the source parameters (M0 and fc) and the attenuation factor t* is carried out using single spectra fitting. We applied this method to earthquakes that occurred in the southern Sichuan Basin. We applied this method to 257 earthquakes with magnitudes ≥1.5 recorded in the Weiyuan area of the southern Sichuan Basin, China, between November 2015 and November 2016. Seismic moments and corner frequencies are obtained through the combined use of spectral ratio analysis and single spectral fitting, from which stress drops are estimated assuming a circular crack model. The resulting t* measurements are subsequently used to invert for the regional attenuation structure, providing an independent evaluation for the robustness of the inferred source parameters. This study was supported by the National Natural Science Foundation of China (42474084).
How to cite: Chang, X., Shen, L., and Zhao, L.-F.: A spectral-ratio-constrained joint inversion of source parameters and attenuation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6910, https://doi.org/10.5194/egusphere-egu26-6910, 2026.
In both geophysics and medical physics, the propagation of seismic waves through highly complex, heterogeneous viscoacoustic-viscoelastic media follows the same physical principles. The attenuation of seismic waves in the Earth's heterogeneous interior is identical to the way ultrasound waves behave when passing through the human skull or bones (transcranial ultrasound).
In this work, we utilize the core concepts of wave physics and spectral element method (SEM), a well-known numerical simulation technique within geophysics that is used to study the scattering and attenuation caused by the skull during transcranial ultrasound. In the Earth, P-waves can convert to S-waves at interfaces; similarly, at the interface of the skull, ultrasound undergo mode conversions, and also generates Lamb waves, which further complicates the energy transmission. Despite the massive difference in physical scale, both medical ultrasound and geophysics involve a similar number of wavelengths between the source and receiver.
The interface between the skull and soft brain tissue creates a high impedance contrast causing most of the energy to reflect and only a small amount of energy is transmitted through skull.
3D numerical phantoms replicating skull-like properties with varying thicknesses were constructed. SEM, a high-order numerical modeling technique, is used for full waveform modeling of both elastic-acoustic and viscoacoustic-viscoelastic waves through heterogeneous media. A conformal hexahedral mesh is implemented to precisely resolve the irregular geometry of the bone. This ensures that the simulated reflections and refractions are physically accurate and thereby avoid numerical staircasing artifacts.
The difference in the amplitude and waveform propagation is studied between the acoustic-elastic and viscoacoustic-viscoelastic mediums. Elastic modeling assumes energy is conserved, while viscoelastic modeling incorporates the quality factor (Q) to simulate intrinsic attenuation.
Amplitude decay measures the difference between the peak pressure value of the transmitted waves. Amplitude decay and difference between wavefields are analyzed to quantify how the heterogeneous internal structure affects the wavefront, and also demonstrating that SEM, a proven geophysical method, effectively simulates and quantifies medical ultrasound wave propagation.
How to cite: Lohan, I., Marty, P., and Fichtner, A.: Quantifying attenuation and scattering in skull-like phantoms using the spectral element method, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8977, https://doi.org/10.5194/egusphere-egu26-8977, 2026.
The collision between the Indian and Eurasian plates has resulted in one of the most tectonically active zones in the world. To characterize the crustal structure and thermal properties of the region, we present a high resolution Lg wave attenuation model along with Lg wave propagation efficiency map for the Indian Shield, the Himalayas, and the Tibetan Plateau and neighbouring areas. Using a dataset comprising more than 1,800 regional earthquakes recorded by 795 broadband seismic stations, we inverted spectral amplitudes using the least squares orthogonal factorization (LSQR) method to map the lateral variation of the Lg wave quality factor (QLg ) and its frequency dependence (η). The resulting tomographic images reveal a sharp contrast in crustal attenuation across the collision zone. The Indian Shield exhibits significant tectonic stability and low attenuation (high QLg ) along with high Lg wave propagation efficiency, consistent with the transmission of seismic energy through a rigid cratonic lithosphere. Conversely, the Tibetan Plateau is dominated by widespread high attenuation (low QLg ) and significantly reduced Lg wave propagation efficiency, with the lowest values observed beneath the Qiangtang and Songpan-Ganzi terranes. The variation in the η parameter highlights the distinction between intrinsic and scattering attenuation, correlating strongly with regional heat flow variations. We observe a clear spatial correlation between low QLg anomalies and the presence of partial melt or aqueous fluids within the Tibetan crust. These results provide new insights into the geophysical understanding of the collision zone and the geometry of the crustal structure.
How to cite: Bose, S., Singh, C., and Singh, A.: Lg Wave Attenuation across the Indo-Eurasian Collision Zone, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10547, https://doi.org/10.5194/egusphere-egu26-10547, 2026.
Myanmar is located at the southeastern margin of the collision zone between the Indian and Eurasian plates, occupying a key position in the Eastern Himalayan Syntaxis. It serves as a natural laboratory for studying oblique subduction, accretionary orogeny, and crust-mantle dynamics. However, the complex crust-mantle kinematic decoupling mechanism in this region, as well as the control of deep slab geometry on magmatic thermal evolution, remain subjects of debate. Since seismic attenuation is highly sensitive to temperature, partial melting, and fluid content, conducting high-resolution attenuation tomography is crucial for revealing the deep physical state of materials and geodynamic processes in this area. In this study, we performed high-resolution 3-D P-wave attenuation tomography of the Myanmar Orogen using seismic data recorded by 70 stations from the China-Myanmar Geophysical Survey in the Myanmar Orogen (CMGSMO I) between June 2016 and February 2018. We utilized 2,313 seismic events obtained from a deep-learning-based catalog and extracted 14,273 high-quality P-wave t* measurements. By employing the trans-dimensional Bayesian Markov Chain Monte Carlo (MCMC) method, we constructed a high-precision 3-D attenuation model of the study region. The inversion results reveal two significant high-attenuation anomalies: a shallow high-attenuation zone beneath the Indo-Burma Ranges (IBR) at depths of 0–40 km, and a deep high-attenuation anomaly beneath the Central Basin at depths of 80–120 km. The shallow high-attenuation zone coincides well with low-velocity structures; we attribute this to high porosity and fluid saturation within the accretionary wedge sediments, as well as fluid overpressure and rheological weakening caused by deep metamorphic dehydration. This rheologically weak layer likely acts as a lower crustal detachment, facilitating kinematic decoupling between the upper crust and the underlying lithosphere. The deep high-attenuation anomaly reflects asthenospheric upwelling triggered by a "slab window" resulting from the tearing of the Indian Plate. The injection of high-temperature material into the mantle wedge induces partial melting and significantly enhances seismic wave attenuation.
How to cite: Feng, Y., Ai, Y., Zhang, Z., He, Y., Jiang, M., Wei, S. S., Mon, C. T., Thant, M., and Sein, K.: New Insight into the Indo-Burma Subduction Zone: Implications from Seismic Attenuation Tomography in Central Myanmar, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12286, https://doi.org/10.5194/egusphere-egu26-12286, 2026.
The Val d’Agri basin in southern Italy is largest onshore hydrocarbon systems in Europe and, at the same time, one of the most seismically active sedimentary basins in the Apennines. This area appears as an ideal natural laboratory for investigating how fluids, rock damage and stress interact in the shallow crust thanks to the production and fluid injection that take place in this oilfield.
We analyze a dense local earthquake dataset recorded in the Val d’Agri area using seismic attenuation tomography. Attenuation is imaged with the MuRAT workflow, a Matlab algorithm that exploits multi-frequency measurements of direct and coda-wave amplitudes to recover three-dimensional distributions of scattering and absorption. These parameters are highly sensitive to fracture density, lithology, and fluid saturation, and therefore provide a physically meaningful view of the reservoir and fault system.
The resulting attenuation volumes allow us to identify zones of strong energy loss and high heterogeneity that may correspond to highly fractured, fluid-rich areas within the sedimentary cover and along major fault systems. Such features are particularly relevant in a georesource context, as they can act both as preferential fluid pathways and as mechanically weak volumes prone to seismic activation. Results of these analyses provide new light on the internal structure of the reservoir and its surrounding fault network, while also highlighting their interaction with industrial operations.
Overall, this work demonstrates how seismic energy attenuation tomography can provide a powerful framework for imaging fluid–fault interactions in active hydrocarbon systems. The results offer new insights into the processes controlling induced and triggered seismicity in the Val d’Agri basin and contribute to the development of geophysically informed strategies for sustainable resource exploitation and seismic risk management.
How to cite: Avella, M., De Siena, L., Garcia, A., and Zaccarelli, L.: Attenuation Tomography Analysis in the Val d’Agri Oilfield, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13919, https://doi.org/10.5194/egusphere-egu26-13919, 2026.
Impoundment of the Baihetan Reservoir has triggered intense micro-seismicity, raising questions about the underlying hydro-mechanical drivers. While stress drop variations suggest fluid lubrication reduces effective normal stress, distinguishing fluid-saturated conduits from dry fracture networks remains challenging with traditional tomography. Standard attenuation imaging (Qt-1) inherently conflates scattering (structural heterogeneity) and intrinsic absorption (anelastic loss), obscuring the true physical state of the subsurface.
To resolve this, we apply Multi-Resolution Attenuation Tomography (MuRAT) to a dense local seismic array dataset. By utilizing Radiative Transfer Theory, we independently invert for scattering (Qsc) and absorption (Qi) attenuation coefficients. Our results reveal a distinct spatial decoupling of these mechanisms. Scattering anomalies (low-Qsc) correlate strongly with the surface traces of the Zemuhe and Xiaojiang fault zones, effectively imaging the pre-existing fracture network. In contrast, intrinsic absorption anomalies (low-Qi) are concentrated at depths of 5–10 km. These high-absorption features are spatially consistent with theoretical zones of fluid infiltration. By separating structural damage from fluid presence, we provide independent geophysical constraints that support fluid-diffusion hypotheses derived from source parameter analysis.
How to cite: Hu, Y., De Siena, L., Liu, R., He, X., and Xu, L.: Attenuation Tomography of the Baihetan Reservoir: Separating Fluids from Fractures in Induced Seismicity, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15304, https://doi.org/10.5194/egusphere-egu26-15304, 2026.
