This session will bring together experts in the field of seismic attenuation. The session will focus on:
• Theoretical and open-source computational advancements in understanding and modelling viscoelastic wave propagation, including seismic scattering and seismic absorption, in heterogeneous media;
• Techniques that utilise seismic attenuation to eliminate trade-offs in seismic source measurements;
• Understanding the impact of seismic attenuation on earthquake ground motion as a function of both distance and frequency;
• Measurements and data processing techniques to obtain total, scattering and intrinsic attenuation parameters within rocks, crustal faults and fractures, and planetary bodies;
• Research linking seismic attenuation to the conversion of energy into other forms, such as heat, especially in the context of geothermal resources and volcanic hazard assessment;
• Tomographic methods using seismic attenuation, scattering, and absorption as attributes, including in combination with seismic velocity, to understand and interpret the Earth's structure and dynamics.
An automatic waveform modeling method to estimate source and attenuation parameters for earthquakes
R. Petito Penna1, A. Zollo1,2, G. Russo2, S. Nazeri2, G. De Landro2
1 Scuola Superiore Meridionale, Napoli, Italia
2 Dipartimento di Fisica Ettore Pancini, Università degli Studi di Napoli Federico II, Napoli, Italia
Seismic waves in the Earth's crust experience attenuation, affecting waveform, amplitude, and duration. Anelastic attenuation is quantified by the quality factor Q, the ratio of energy lost per wave cycle to total radiated energy. Kjartansson (1979) developed a model where Q is spatially variable but frequency-independent, predicting a linear relationship between pulse width Tdc and the attenuation parameter tc* :
Here, c refers to P or S phase, Tdc is the pulse duration at the receiver, T0 is the apparent source duration, TTc is the travel time, and Qc is the quality factor. Cdc is a constant coefficient. This relation also applies to half duration Thdc, defined as the time between the pulse peak and its beginning.
We propose a time-domain technique to estimate source parameters and Q by measuring pulse durations (Tdc and Thdc) for P- and S-wave displacement signals in an anelastic medium. These signals are recorded at stations around epicenters with a known velocity model. Based on circular kinematic rupture models (Sato and Hirasawa, 1973; Madariaga, 1976), our method approximates the far-field displacement waveform with a scalene triangular function and finds the theoretical waveform that best fits the recorded P (or S) pulse.
For each seismic station, the procedure reads three ground motion records, calculates the displacement modulus, and detects P and S phase arrivals using a kurtosis-based technique (Ross et al., 2014). It selects a time window around each phase, searching for the best-fit triangular waveform by adjusting total duration Tdc, half duration Thdc, and peak amplitude AP. A cross-correlation function aligns real and theoretical signals, calculating the cost function:
where N is the window length, n is the time instant, AReal is the real signal amplitude, and ATheo is the theoretical amplitude. The [i, j, k] indices correspond to the i-th value of Tdc, the j-th value of Thdc and the k-th value of AP. The best-fit signal corresponds to the smallest F value, repeated across stations.
The next step is to fit total durations to travel times to estimate T0 and stress drop Δσ from the slope, providing information about the ratio Cdc/Q. Applying this to 500 earthquakes (0<Mw<4) in Nagano, Japan (November-December 2014), we found average stress drops of <ΔσP>=(0.09±0.05)MPa for P-waves and <ΔσS>=(0.04±0.03)MPa for S-waves, with average Q values <QP>=143±14 and <QS>=340±133. Cdc was set to 1.
Kjartansson's model assumes Cdc is independent of Q, stress-drop ∆σ, and magnitude M. However, our analysis on synthetic triangular signals suggests these dependencies are present. Validating these dependencies with real signals is crucial. We show it's possible to test Cdc's dependency on magnitude, stress-drop, and Q by combining waveform fitting results with signal spectrum modeling, extending the proposed methodology's applications.
How to cite: Petito Penna, R., Zollo, A., Russo, G., Nazeri, S., and De Landro, G.: An automatic waveform modeling method to estimate source and attenuation parameters for earthquakes , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12495, https://doi.org/10.5194/egusphere-egu25-12495, 2025.
In local earthquake seismology depth-dependent elastic models of P- and S-wave velocities are indispensable, e. g. to locate earthquakes. If not only travel times but also amplitudes of seismic waves are important, elastic Earth models are insufficient and visco-elastic models are required to include intrinsic absorption of seismic waves. This applies e. g. to the estimation of moment magnitudes and to physics-based ground motion modeling in seismic hazard analysis. The estimation of seismic attenuation parameters of the Earth is significantly more difficult than the estimation of velocities for two reasons: (1) Scattering attenuation as well as intrinsic absorption contribute to the attenuation of seismic waves and it is essential to separate these two effects. (2) Seismic attenuation parameters are inherently frequency dependent, whereas the frequency dependence of seismic P- and S-wave velocities can be neglected in almost all cases. Due to the lack of information, attenuation is often completely neglected in seismic wave simulation, standard values for seismic Q are used, or frequency dependence and depth dependence are ignored. To solve this issue, we develop a computer code, 'QEST - Q estimation'. The code is based on a forward modeling using radiative transfer theory in depth-dependent velocity and attenuation models and a global inversion scheme based on a genetic algorithm. Besides frequency and depth dependent intrinsic as well as scattering attenuation parameters, earthquake source spectra and frequency dependent site amplifications are also a result of the inversion with QEST. We applied the technique to seismograms of earthquakes in three regions: the Upper Rhine Graben (Germany), the Leipzig-Regensburg fault zone (Germany) and the Alaska Subduction Zone (Alaska). These regions were selected to represent exemplary areas with thick sedimentary layers, without thick sedimentary layers and the lithosphere and asthenosphere, respectively. Results show a clear depth and frequency dependence of both, scattering attenuation as well as intrinsic absorption, within the thick sediments of the graben. In contrast, the Leipzig-Regensburg fault zone exhibits a clear frequency dependence of the attenuation parameters, albeit only a smaller depth dependence, while the results of the Alaska Subduction Zone show a depth and frequency dependence that is particularly evident in the scattering attenuation.
How to cite: van Laaten, M. and Wegler, U.: Intrinsic and Scattering Attenuation of Shear Waves: Depth- and Frequency-Dependent Attenuation Insights using the QEST Code, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8259, https://doi.org/10.5194/egusphere-egu25-8259, 2025.
An accurate magnitude estimation is necessary to evaluate properly the seismic hazard. Unfortunately, the magnitudes of small earthquakes are subject to large uncertainties due to high-frequency propagation effects, which are generally not accurately considered. To address this issue, we developed a method to separate source, attenuation and site parameters from the elastic radiative transfer modeling of the full energy envelopes of seismograms. Our separation method is based on a 2-step inversion procedure. First, for each source-station pair, we retrieve the optimal frequency-dependent attenuation parameters (scattering and absorption) fitting the observed energy envelopes in the 0.375-24Hz band. In a second step, we separate the source and site amplification spectra using a joint inversion algorithm. The site amplification is adjusted on reference stations, characterized by approximatively flat H/V ratios. From the source spectra, we estimate the moment magnitude Mw, the corner frequency fc and the apparent stress σapp.
We applied the inversion procedure to around 21000 waveforms recorded by EPOS-FR and LDG stations at hypocentral distances less than 250 km, for earthquakes with magnitudes ML ranging from 2.0 to 5.9. The magnitudes Mw of the extracted 1300 source spectra show a high coherency of our inverted Mw with the unified Euro-Mediterranean catalogue. The comparison with the SI-Hex catalogue shows the role of attenuation variations across France in source parameters estimation. These spatial variations of attenuation are highlighted through scattering and absorption maps. σapp reveals a slight increase with Mw, but no regional differences when preforming the joint inversion. On the contrary, if source and site parameters are estimated for each event independently, σapp presents spatial variations with a systematic higher level in Western France. This regional difference is caused by a regional site effect not considered in a disjoint separation scheme in space and time across the event catalog. These results show the importance of attenuation and site correction in estimating source parameters. In the future, we intend to automate our method and apply it routinely to smaller earthquakes for which traditional methods are not readily applicable due to the complexity of waveforms.
How to cite: Heller, G., Sèbe, O., Margerin, L., Traversa, P., Mayor, J., and Calvet, M.: Generalized inversion of source, site and attenuation parameters using the radiative transfer theory: application to a French dataset, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10969, https://doi.org/10.5194/egusphere-egu25-10969, 2025.
The fault damage zone is a region surrounding an earthquake fault interface where rocks are significantly fractured due to tectonic movements and historical large earthquakes on the fault. The rock fractures within the damage zone absorb and scatter seismic waves, causing amplitude decay in different frequency ranges. In this study, we use ambient noise attenuation tomography to image the fault damage zones in two tectonic settings: a transform fault in southern California and a thrust fault in western Sichuan. According to dynamic rupture models, a preferred rupture direction leads to asymmetric damage zones adjacent to the fault interface. In the Ramona array example for the San Jacinto Fault, the velocity contrast across the strike-slip fault interface leads to a preferred rupture direction towards northwest, resulting in more pronounced damage on the side with higher-velocity at depth. In the Hongkou array example for the Longmenshan Fault, significant rock damage is observed at ~ 1 km depth in the footwall side of the thrust fault interface due to upward rupture propagation from seismogenic depths. Combined with ambient noise differential adjoint tomography, a more detailed S-wave velocity model can be derived, facilitating the interpretation of tectonic structure across the fault interface and further constraining the asymmetric nature of the observed fault damage zones as predicted by dynamic rupture models.
How to cite: Liu, X., Beroza, G., Ben-Zion, Y., and Li, H.: Revealing fault damage zones using ambient noise tomography, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3594, https://doi.org/10.5194/egusphere-egu25-3594, 2025.
Understanding the distribution of fluids in subsurface reservoirs within volcanic systems is important for geothermal energy development, the exploration of critical-metal-bearing brines, and other applications, including forecasting volcanic eruptions. Seismic attenuation tomography can be used to map fluids and structural features beneath a volcano. Here, we use coda wave attenuation and peak delay time, which measure absorption and scattering, respectively, at the Aluto volcano. Aluto volcano is located in the central part of the Main Ethiopian Rift (MER) and is Ethiopia’s first pilot site for geothermal exploration. Absorption is highly effective in detecting fluids, high temperatures, and melt, while scattering is effective in detecting lithological variations and structural features such as faults and fracture systems. We analysed seismic data from January 2012 to January 2014, locating 2,393 events that predominantly lie along the Wonji Fault Belt (WFB) using non-linear location methods. We selected 312 events for 3D attenuation tomography based on the number of phases and a coda-to-noise ratio of three or higher. High inverse coda quality factor is spatially correlated with high-temperature areas, zones with hydrothermal manifestations and elevated CO2 flux, and around productive geothermal wells with high temperature and high enthalpy. High scattering is spatially correlated with areas of structural features such as faults and fracture systems, which act as fluid pathways and with the most permeable geothermal wells. These methods better constrain the distribution of fluids, high-temperature areas, and lithological and structural variations and can be used in geothermal exploration. High absorption and scattering areas are ideal for geothermal exploration, as they indicate hot fluids in fractured permeable rock.
How to cite: Yemane, T., Kendall, J. M., Gabrielli, S., and De Siena, L.: Seismic Absorption and Scattering Imaging at Aluto Volcano in the Main Ethiopian Rift, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13642, https://doi.org/10.5194/egusphere-egu25-13642, 2025.
Seismic wave characteristics are influenced by several physical processes, including the
earthquake source, geometrical effects such as topography, and local amplification phenomena.
In urban environments, civil structures introduce an additional complexity in the wavefield
evolution. While earthquake engineers have traditionally regarded buildings as passive
recipients of seismic waves, diverse seismological studies have demonstrated that building
clusters can significantly alter the ground motion (e.g. Guéguen et al. 2002; Kham et al.
2006; Semblat et al. 2008; Guéguen & Colombi, 2016). This phenomenon is known as
site-city interaction (SCI) effects. Key signatures of SCI include elongated ground motion
duration, increased spatial variability, and wave amplitude decay. SCI arises from two primary
mechanisms: kinematic and inertial interactions. In kinematic interaction, seismic waves are
scattered due to the impedance contrast between the soil and the building foundations. In
inertial interaction, the wavefield is perturbed at frequency bands near the resonant frequencies
of the buildings, often converting surface into body waves or adding some harmonics. Despite
extensive studies using numerical simulations and observations either from active shots or
earthquake records, the contribution of SCI mechanisms to seismic wave attenuation remains
insufficiently quantified.
In this work, we use 3D numerical simulations to study the wavefield evolution in urban
environments at the local scale, for frequencies up to 10 Hz. Simulations are performed by
using the spectral element method code EFISPEC (De Martin, 2011). The model consists of a
layered half-space with a flat surface, where the shear wave velocity of the layer is 200 m/s
and that of the half-space is 650 m/s. The urban configuration includes 30 buildings spaced
100 m apart, each 100 m high. The building foundations are modeled as rigid blocks with size
25 m. We perform three sets of simulations: (1) free-field conditions, (2) with foundations
only, and (3) with complete buildings. Attenuation is quantified from the amplitude decay
of the ballistic wavefield with distance. Our results reveal that at high frequency (> 5 Hz),
seismic wave attenuation is primarily controlled by scattering, driven by interactions with
foundations acting as diffractors. At lower frequencies, attenuation is dominated by the
building dynamics, resulting in energy band gaps near the modal frequencies of the buildings.
Additionally, the scattering attenuation length is found to be of the same order as the spacing
between foundations.
How to cite: Celorio, M., Guéguen, P., Aochi, H., De Martin, F., and Bonilla, F.: Seismic wave attenuation in urban environments: insights from 3D numerical simulations of site-cityinteraction, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17608, https://doi.org/10.5194/egusphere-egu25-17608, 2025.
Layering or stratification, as well as volume (spatial) heterogeneity and rough boundaries between the layers (the interface roughness), are ubiquitously present in natural environments and caused by combination of many processes, for instance, by regular gravity-controlled vertical sedimentation, as well as continuous and discrete irregularity due to granular microstructure, presence of solid inclusions, gas bubbles, voids, and spatial fluctuations of their volume concentration. In this paper, we consider wave propagation, scattering, and attenuation in a stack of elastic layers with various types of irregularities (or scattering mechanisms), represented by volume heterogeneity within the layers and roughness of the interfaces in between, and given by spatial continuous and discrete variations of material parameters. A general idea of suggested here theoretical approach originates from one used in acoustics to consider underwater sound propagation for calculating the coefficient of reflection of compressional plane waves from a stack of fluid homogeneous layers with flat interfaces (modeling, for example, discretely stratified water-like sediments) using the reflection coefficients of each interface. We show that a similar, but a more general matrix approach, can be developed to include scattering mechanisms, such as interface roughness and volume heterogeneity, as well as different types of media and waves, for instance compressional and shear seismic waves (vertically and horizontally polarized) in elastic, viscoelastic, and poroelastic layers. A general full-wave solution for an arbitrary number of such layers is described in terms of transition matrix coefficients, or T-matrixes, taken from a set of simpler solutions for a plane wave transformation, reflection and scattering from, and transmission through, a single layer located between two homogeneous half-spaces and therefore isolated from interactions with other boundaries. Inside of this layer, for simplicity, scattering mechanisms are isolated as well - either a rough interface or volume heterogeneity is allowed. These simplified T-matrix solutions (found separately for each “isolated” layer and interface of the system) provide inputs to a set of integral equations which describe interactions between different layers and interfaces. Then a general solution, the scattering amplitude or T-matrix of the whole stack of layers can be obtained using an iterative procedure that starts from a simple case of two half-spaces at the basement. As an example, scattering from a heterogeneous elastic layer is considered resulting in explicit expressions for the coherent reflection loss and the incoherent scattering strength. Applications to remote sensing of underwater sediments and sea ice are discussed. [Work supported by ONR and BSF].
How to cite: Ivakin, A.: Modeling of wave propagation in multi-layered environments with rough interfaces and volume heterogeneities: A T-matrix approach, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7512, https://doi.org/10.5194/egusphere-egu25-7512, 2025.
Anelasticity is an intrinsic property of the Earth that causes energy reduction of propagating seismic waves. Accurate 3D anelastic full waveform modeling and inversion are important for imaging high resolution velocity and attenuation structures of the Earth, which will provide crucial insights into the plate tectonics and geodynamic processes. In the presence of strong attenuation, wavefield simulation requires a strong stability preserving time discretization scheme. Otherwise, wavefield simulation could be inaccurate or unstable over time if not well treated. In this work, we choose the optimal strong stability preserving Runge Kutta (SSPRK) method for the temporal discretization and apply the fourth order MacCormack scheme for the spatial discretization. Theoretical and numerical analyses show that, compared with the traditional fourth order Runge-Kutta method, the SSPRK has a larger stability condition number and can better suppress numerical dispersion. As a result, our method can largely improve the computational efficiency during numerical modeling. Based on our forward anelastic modeling method and in the framework of the scattering integral method, we develop a new method for computing the 3D waveform sensitivity kernels that accounts for full physical-dispersion and dissipation attenuation. The Northwestern United States region is chosen as an example to verify the accuracy of the computed 3D velocity and attenuation sensitivity kernels. Finally, we construct a 3D high resolution model of velocity and attenuation structure of the crust and upper mantle in Eastern Tibet using real seismic waveform data, which provides important constraints on the processes of crustal and mantle extrusion in Eastern Tibet.
Acknowledgments
Nian Wang is supported by the National Natural Science Foundation of China (42204056) and China Postdoctoral Science Foundation (2021M690087).
How to cite: Wang, N., Shen, Y., and Yang, D.: 3D anelastic full waveform modeling and inversion, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5308, https://doi.org/10.5194/egusphere-egu25-5308, 2025.
The energy on the seismogram before the arrival time of the seismic main PP wave is called PP precursor. Although the name of PP precursor corresponds to the term PP, the components do not only concern the wave reflection back from the surface. The early part of the PP precursors overlapped with the P or Pdiff wave coda, meanwhile the PKiKP wave arrived earlier than the PP wave when the distance is larger than about 100°, which results in a mixture with the PKiKP phase. The origin of the PP precursors was usually regarded as the discontinuities of the mantle, like 410 km and 660 km discontinuities. However, the arrival time and the slowness from seismic array beamforming of the precursors very close to the PP wave both disagree with this interpretation. Some middle mantle reflection layers (e.g., at 1000 km) may contribute to the unknown phase before the PP wave at the long period, but cannot explain the gradually increasing energy before the phase at high frequency. We have observed the PP precursors at high frequencies of 1–2 Hz at an epicentral distance between 95° and 115° from the earthquakes whose magnitude is larger than 7.0 Mw and the source depth is shallower than 100 km. The global PP precursors show that it originates not only from the off-great-circle scattering at some regional subduction slabs. The stacking result is compared to our Monte Carlo simulation of 3D scattering with a 1D spherically symmetric heterogeneity model, which has much potential to be improved. Single scattering of the middle and upper mantle (shallower than 1000 km depth) allows for the generation of the emerging PP precursor at high frequencies. The scattering process is similar to the one responsible for the generation of the Pdiff coda, which is generated by scattering in the whole mantle. As a consequence, the scattering pattern of the PP precursors is PP*P or P*PP, where the asterisk indicates the scattering, which explains that the slowness of some PP precursors is higher than the PP wave but sometimes similar to the P or Pdiff wave.
How to cite: Zhang, T. and Sens-Schönfelder, C.: New Insights about the Character of the PP Precursors at High Frequency, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15677, https://doi.org/10.5194/egusphere-egu25-15677, 2025.
3D attenuation tomography of the upper mantle is important for understanding the temperature and rheological structures of the Earth’s interior as well as the related geodynamic features and mechanisms. However, robust surface-wave attenuation tomography is still challenging due to the strong trade-off between the intrinsic attenuation and the scattering due to the complex effects of 3D wave-speed and density heterogeneities in the surface-wave amplitude records. Based on tracking surface-wave travel times and amplitudes from seismic array data, here we upgraded the theory of Helmholtz tomography by accounting for the scattering effects and present a new method called Helmholtz Multi-Event Tomography to invert for the variation of surface-wave attenuation. The synthetic inversions based on 3D forward simulations in anelastic media validate the effectiveness of our new method. We then demonstrated the resulting surface-wave attenuation model can be applied to an iterative depth inversion that reveals the 3D variation of intrinsic attenuation of the upper mantle. Our study provides an innovate and promise way to generate accurate and precise attenuation models of the upper mantle from surface-wave data with low computational cost.
How to cite: Bao, X. and Wang, N.: Upper-Mantle Attenuation Tomography Using Surface Waves Recorded by Regional 2D Seismic Arrays, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5378, https://doi.org/10.5194/egusphere-egu25-5378, 2025.
The details of heterogeneities in the lower mantle have increased considerably during the last decades thanks to seismic imaging revealing ULVZs, D” layer, PERM anomaly and now mega-ULVZs. However, the origin of these anomalies is actively debated, as seismic velocities alone cannot disentangle between thermal or compositional origins. Seismic attenuation can provide an additional perspective to seismic velocity for constraining physical properties of the lower mantle heterogeneities. In this study, we aim to develop the first 3D global model of body wave attenuation (Q) in the lower mantle using various S-phase measurements. To maximize the depth and spatial coverage, we incorporate multiple phases (S, SS, SSS, SSSS), core phases (ScS, ScSScS, ScSScSScS), Sdiff and their depth phases (e.g., sS, sScS, sSdiff). We process > 80, 000 seismic data recorded on more than 2000 global seismic stations from earthquakes occurring during 2009-2023. We measure differential anelastic delay times between the observed S phases and the same phases on 3D synthetics using the instantaneous frequency matching method in period range of 100 ~ 10 seconds. These synthetic seismograms are computed in 3D mantle model S40RTS and crust model CRUST1.0 using SPECFEM3D-globe, which can fully account for the effect of 3D heterogeneities, allowing for reliable attenuation measurements. The differential anelastic time delays exhibit abnormally large variations for all S phases, reflecting the complexity of the data potentially brought by the elastic effects. Despite this, the average differential anelastic time delays for all S phases remain consistently negative across all epicentral distances and generally decrease with increasing epicentral distances, suggesting that the Earth is, on average, less attenuating than the PREM model. We further find that the scattering of differential anelastic time delays can be significantly reduced, and abnormal measurements effectively excluded, when the waveform similarity of observed and synthetic phases is high. This is likely because, in such cases, uncertainties arising from factors like source mechanisms and heterogeneity are substantially minimized. We perform a 1D tomographic inversion using high-similarity data. The preliminary 1D attenuation model we obtain is similar to PREM model, with lower attenuation in the lower mantle and the highest attenuation in the upper mantle, roughly corresponding to the depth range of the low velocity zone. However, the Q values in our model are approximately 1.5 times larger than the Q values in PREM model. Next, we will perform 3D tomographic inversion and subsequently integrate this 3D Q model with global 3D shear wave models to jointly invert for the thermo-chemical state of the lower mantle.
How to cite: Sun, S., Durand, S., Ricard, Y., and Debayle, E.: Global Lower Mantle Attenuation Model and the Origin of Lower Mantle Seismic Heterogeneities, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8713, https://doi.org/10.5194/egusphere-egu25-8713, 2025.
Surface or shallow subsurface water and ice have been reported on Mars, but sustaining life requires more than just the presence of liquid water. A mechanism to preserve water over geological timescales is essential, and a deep-water reservoir could fulfill this role. However, the volatile content of Mars’ deeper mantle remains poorly constrained. Using seismic data from global tectonic marsquakes and meteorite impacts recorded by the InSight mission, we observed weak attenuation in Mars’ deep mantle (500–1500 km) relative to Earth’s. This weak attenuation likely results from lower water content, larger grain size, and/or reduced oxygen fugacity in the martian mantle. Assuming mantle mineral grain sizes on Mars are similar to those on Earth, Mars’ upper mantle appears relatively dry, with water content estimated at less than 13–24% of Earth’s. If deep water exists on Mars today, it is most likely confined to the basal mantle layer (~ 1550–1700 km) at the core-mantle boundary, potentially the only viable deep-water reservoir for the red planet.
How to cite: Li, J.: Evidence for Weak Attenuation in Mars’s Deep Mantle, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4001, https://doi.org/10.5194/egusphere-egu25-4001, 2025.
The North China Craton (NCC) was formed from the Archean to the Paleoproterozoic and is one of the oldest cratons in the world, which can be divided into three parts: the Western Block, the Eastern Block, and the Central Orogenic Belt. Since the Mesozoic, the NCC has experienced significant destruction and transformation, and has developed a large number of extensional structures, accompanied by intense magmatic activity, metal minerals and oil and gas resources. Many seismic velocity tomography studies have been conducted in NCC, however, there are very few seismic attenuation tomography studies in the region. For this reason, this study collects P- and S-wave seismograms from ~6,000 earthquakes recorded by 477 permanent and 111 temporary stations in North China from 2013 to 2017, and uses body wave attenuation tomography to determine its three-dimensional attenuation structure of the crust and uppermost mantle.
We first use the seismic amplitude spectrum to determine about 60,000 P-wave t* and 57,000 S-wave t* data, and use the spectrum ratio method of Guo and Thurber (2021) to construct event-pair differential t* data. By using both absolute and differential t* data, we determined 3D Qp and Qs models of the NCC lithosphere with grid intervals of 0.5°×0.5° in the horizontal directions and 10 km in the depth. Overall. the Q features in the crust correspond well to the regional geological structures. In the shallow depths, thicker sedimentary zones are associated with low Q values, such as the Bohai Bay Basin and the western part of the Central Orogenic Belt (COB). Relatively low Q values are also associated with fault zones, such as the Tanlu fault zone and the Zhangbo fault zone. In addition, the Hetao rift and the Weihe rift zones also have relatively low Q values. Beneath the Datong volcanic field, evident low Q values extend from the crust to the upper mantle, suggesting the existence of partial melting.
In comparison, the Yanshan orogenic belt has significantly higher Q values. In the uppermost mantle, both Qp and Qs models have high values in the eastern part of the NCC, and the COB and western part have lower Q values. Across the North-South Gravity Lineament, there is a sharp change of Q values with lower to the west and higher to the east. We will combine Qp and Qs models with the available velocity models to further understand the destruction and dynamic processes of the NCC.
How to cite: Zhang, H. and Wang, J.: Three-dimensional seismic body wave attenuation tomography of the North China Craton : implications for craton destruction and transformation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8983, https://doi.org/10.5194/egusphere-egu25-8983, 2025.
Understanding Lg wave attenuation provides valuable insights into crustal properties such as temperature, partial melting, and fractures, making it a crucial tool for studying crustal material flow in tectonically active regions. Central-southwestern China, encompassing the eastern Tibetan Plateau, Sichuan Basin, Qinling Orogenic Belt, and nearby areas, is a key region for such research due to its complex tectonic activity driven by the collision between the Indian and Eurasian plates. However, many questions remain about the pathways and barriers that influence the eastward migration of crustal material from the Tibetan Plateau. To tackle these challenges, we treat unresolved 3-D structural effects in Lg spectral amplitude as Gaussian-distributed modeling errors. This approach supports our SVD-based inversion method, enabling reliable estimation of crustal attenuation and thorough evaluation of model resolution and reliability. By incorporating site response corrections into the traditional two-station (TS) method and integrating it with reversed two-station (RTS) and reversed two-event (RTE) techniques, we effectively minimized the impact of source and site effects, enhancing the accuracy of attenuation tomography. Utilizing over 34,000 Lg waveforms from 257 crustal earthquakes, we constructed a high-resolution broadband Lg wave attenuation model across a frequency range of 0.05–10.0 Hz. The findings reveal complex attenuation patterns that correlate with regional tectonic and crustal features, offering fresh insights into the pathways and barriers affecting the eastward flow of material from the Tibetan Plateau.
How to cite: Hu, Y., Chen, Y., and Liu, R.: Two-station Lg wave attenuation tomography in Central-Southwest China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-718, https://doi.org/10.5194/egusphere-egu25-718, 2025.
The Wave Gradiometry Method (WGM) measures spatial gradients of the wavefield within a subarray to extract phase velocity, wave propagation direction, amplitude perturbation, and radiation pattern within a subarray (Langston, 2007; Cao et al., 2020; Liang et al., 2023). The phase velocity can then be analyzed with respect to azimuths to determine azimuthal anisotropy. The Azimuth-Dependent Dispersion Curve Inversion (ADDCI, Liang et al., 2020) method is used in conjunction with the WGM to extract both 3D velocity and 3D azimuthal anisotropy. Amplitude perturbation accounts for geometrical spreading relative to propagation distance, intrinsic attenuation, and wave scattering within the medium. By eliminating the effects of scattering and geometrical spreading, the dispersion curve of attenuation is obtained, allowing for the determination of the medium's 3D attenuation.
The method is applied to the seismic waveforms collected by the ChinArray conducted in the southeastern Tibetan plateau. The arrays have an average station spacing of 35km. Our results show large variations in fast propagation directions (FPD) and magnitude of anisotropy (MOAs) with depths and blocks. The FPDs are positively correlated with plate moving directions measured by GPS. Low-velocity zones (LVZs) in the middle to lower crust are widely distributed in the Songpan Ganze Terrane and the north Chuan-Dian block. However, the LVZs are not well represented across the Lijiang-Xiaojinghe fault towards the southeastern Tibetan plateau. Low 1/Q values are found in the Sichuan basin and Emeishan Large Igneous Province at all depths. For the Tibetan plateau, low 1/Q values are found at depths shallower than 50km, while high 1/Q values are present at 50km and deeper depths. The low attenuation, combined with the FPDs being dominantly perpendicular to the movement directions of the materials, contradicts the lower crust flow model. However, the pure shearing crust shortening model, which involves the thrusting and folding of the upper crust and the lateral extrusion of blocks, may be the primary mechanism responsible for the growth of the southeastern Tibetan Plateau.
References：
Liang, C., Cao, F., Liu, Z., & Chang, Y. (2023). A review of the wave gradiometry method for seismic imaging. Earthquake Science, 36(3), 254-281. https://doi.org/10.1016/j.eqs.2023.04.002
Cao, F., C.Liang*, Yihai Yang, Lu Zhou, Zhiqiang Liu, Zhen Liu (2022). 3D velocity and anisotropy of the southeastern Tibetan plateau extracted by joint inversion of wave gradiometry, ambient noise, and receiver function, Tectonophysics, https://doi.org/10.1016/j.tecto.2022.229690
Liang, C., Liu, Z., Hua, Q., Wang, L., Jiang, N., & Wu, J. (2020). The 3D seismic azimuthal anisotropies and velocities in the eastern Tibetan Plateau extracted by an azimuth‐dependent dispersion curve inversion method. Tectonics, 39, e2019TC005747. https://doi.org/10.1029/2019TC005747
Langston C A. Wave gradiometry in two dimensions (2007). Bulletin of the Seismological Society of America, 97(2): 401-416, https://doi.org/10.1785/0120060138
How to cite: Liang, C. and Cao, F.: The 3D attenuation and anisotropy structure extracted by the Wavegradiometry method resolves the uplift mechanism of the southeastern Tibetan Plateau, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2351, https://doi.org/10.5194/egusphere-egu25-2351, 2025.
The NW Himalayan "seismic gap" spanning the meisoseismal zone of the 1555-Kashmir earthquake, is located between the rupture zones of the 1905 and 2005 earthquakes. Knowledge of the lateral variation in seismic attenuation across this orogenic belt is crucial to estimate ground shaking from future earthquakes. To this end, we use recordings from the Jammu and Kashmir Seismological NETwork to compute the 3D S-wave attenuation (through coda-normalization) and, jointly separate and map the frequency dependent seismic absorption (from coda quality factors) and scattering (from peak delay times) contributions. Our findings reveal strong variations in these parameters throughout the region which are controlled by the differences in crustal structure and rheology. Maps at shallow depths show patches of both high and low attenuation throughout the Sub-Himalaya and the Lesser Himalaya relating to differences in sediment thicknesses or rheology. The regions adjoining the reentrants of MFT south of the Reasi Thrust, and those of the MBT and MCT, SW and SE of the Kishtwar Window display high absorption characteristics, conspicuous across all frequencies and this pattern does alter significantly as depth increases (~20 km). The Kishtwar window, hosting crystalline rocks, is marked by lower attenuation overall but higher attenuation in patches to the south and north, as we go deeper. Surprisingly, high absorption of energy is visible throughout the window across all frequencies. SW of the window, near the MCT reentrant, a broad patch of high absorption coincides with the lateral ramp of the MHT and continues all through in the SE direction. The Kashmir Valley, where sedimentary rocks overlie the crystalline basement shows lateral variations of low and high Q and Qc (absorption), with the Pir Panjal Ranges to its south showing high S-wave attenuation, low absorption and high scattering. At greater depths however this entire zone is marked by high attenuation, high absorption but low scattering which may be a signature of the structure of the top of the underthrusting Indian Plate and/or the frontal-lateral ramps on the MHT.
How to cite: Chaudhuri, D., Kumar, A., Mitra, S., Wanchoo, S., and Priestley, K.: 3D Scattering and Absorption Imaging of the Jammu and Kashmir Himalaya, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9352, https://doi.org/10.5194/egusphere-egu25-9352, 2025.
This study investigates the three-dimensional seismic velocity and attenuation structures of the eastern Sino-Korean Craton through the analysis of an extensive dataset from China and South Korea. The dataset comprises 87,260 earthquakes recorded by 680 Chinese seismic stations since 2008 and 5,400 earthquakes recorded by 483 South Korean stations since 2017. The methodological framework includes 1D velocity model inversion, event relocation, and manual picking of Pg, Pn, Sg, and Sn arrivals, assisted by a machine-learning-based picking approach. A modified ray-tracing technique, optimized for tracking later Pg and Sg arrivals, is employed in double-difference velocity tomography to construct the velocity model. Attenuation factors (t*) for P-waves and S-waves are estimated via source spectral analysis. These factors, combined with the velocity model and arrival time data obtained in velocity tomography, are integrated into attenuation tomography. The dense coverage of seismic ray paths across the Yellow Sea and Bohai Sea enhances resolution, particularly in the boundary regions between mainland China and the Korean Peninsula.
The results identify a high-velocity zone extending from the Sulu Orogenic Belt northeastward through the northern and central Yellow Sea to the western Korean Peninsula, corresponding to the collision zone between the Yangtze and Sino-Korean blocks. Additionally, a low-velocity zone is observed from the crust of the South Yellow Sea to the mantle beneath Halla Volcano, suggesting post-collision extensional processes in the southern Yellow Sea Basin and a potential connection to volcanic activity. Preliminary seismic attenuation results exhibit features generally consistent with the velocity structure, providing insights into the region’s geodynamic evolution and comprehensive understanding of its tectonic and geological history.
How to cite: Liu, Y., Hong, T.-K., Lee, J., Park, S., Celis, S., Lee, J., and Kim, B.: 3D Seismic Velocity and Attenuation Structures of the eastern Sino-Korean Craton, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5292, https://doi.org/10.5194/egusphere-egu25-5292, 2025.
This study investigates the high-frequency attenuation parameter kappa (κ), an important parameter in seismic hazard assessment and ground-motion modeling. Using the BELSHAKE ground-motion database, κ values were first determined from acceleration Fourier amplitude spectra following the classic Anderson and Hough definition. Three fitting methods for estimating site-specific kappa (κ0) of all stations and the regional kappa gradient (κr) in different crustal domains in Belgium were evaluated, the Free Kappa Gradient Method, the Joint Kappa Gradient Method, and the Mixed-Effect Method, and we compared their effectiveness in robustly capturing variations in seismic attenuation. Data from four crustal domains were analyzed, with a filtering process excluding kappa values from induced earthquakes and short-distance, shallow-depth records to enhance the κ-distance relationship and refine κ0 and κr estimation. Our results indicate that the Mixed-Effect Method yields the most robust and reliable estimates. In comparison, the Joint Kappa Gradient Method offers a balance between accuracy and consistency, while the Free Kappa Gradient Method is more sensitive to data availability. This comprehensive analysis advances the estimation of crustal attenuation properties in Belgium, supporting the development of improved seismic models and hazard assessments.
How to cite: Onvani, M. and Vanneste, K.: Analysis of the site-specific and regional components of kappa across crustal domains in Belgium based on the BELSHAKE database, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17631, https://doi.org/10.5194/egusphere-egu25-17631, 2025.
The site response is critical for accurately estimating source parameters, as it directly influences the spectral characteristics of seismic signals. Achieving reliable estimates of these parameters requires clearly distinguishing between source effects, path attenuation, and site response, which are often interdependent and subject to significant trade-offs. As highlighted in recent studies, site response reflects the amplification or damping effects of the shallow subsurface layers on seismic waves, and its accurate characterization is essential to correct the observed spectra and to improve the source parameter estimations. By accurate analysis of the site response, we aim to mitigate these uncertainties and achieve a more robust parameterization of seismic events, particularly for low-magnitude earthquakes, where these effects are more pronounced.
We analyzed the site response of seismic events during the 2016 Amatrice-Visso-Norcia, Central Italy, seismic sequence focusing on earthquakes with local magnitude Ml<2. All seismograms, recorded by the huge INGV-BGS seismic network that consists of 155 recording sites accounting for permanent and temporary seismic stations, were sampled at 100 Hz. We therefore assume that spectral decays are dominated by path attenuation, as corner frequencies are expected to be beyond 40 Hz, the upper limit of the observable frequency range.
The study spans from August 24 to November 30, 2016, and focuses on data from five seismic stations (NRCA, LNSS, SMA1, CAMP, RM33) located within the area hit by the seismic sequence. We selected these stations since they are representative of the activated fault system and lay on different geological units that are separated by a peculiar tectonic line that crosses the epicentral area. We performed a preliminary fit for all events, calculating, for each spectrum that exceeded the signal-to-noise ratio (S/N) threshold, the low-frequency level (Ω0) and the t* attenuation parameter. This analysis was conducted while neglecting the corner frequency (fc) and assuming that the quality factor (Q) is frequency-independent. The amplitude residuals between the observed and modeled spectra for P- and S- waves, derived using the spectral residual technique, were used to calculate the site responses at the five stations. We derive the S/P amplitude ratios in time to highlight also the evolution of the site response at discrete frequencies during an ongoing sequence.
The results provide valuable insights into the spatial and temporal variability of site-specific attenuation effects, emphasizing the dynamic role of subsurface conditions in shaping seismic wave propagation. These findings enhance our understanding of subsurface dynamics in the central Apennines and contribute to more accurate seismic hazard assessments and improved modeling of regional seismicity.
How to cite: Attolico, A., De Gori, P., Anselmi, M., Lucente, F. P., and Tinti, E.: Temporal and spatial variability of site response during the 2016-2017 Amatrice-Visso-Norcia seismic sequence, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12643, https://doi.org/10.5194/egusphere-egu25-12643, 2025.
We perform the attenuation local earthquake tomography (P,S, waves) of the complex fault system that ruptured a wide portion of the central Apennines, during the long lasting seismic sequence that started in 2016. Three mainshocks (the 24 August Mw 6.1, the 26 October Mw 5.9, and the 30 October Mw 6.5) hit the towns of Amatrice, Norcia and Visso causing several casualties and diffuse damages. The ruptured faults spread over an 80 km north-northwest-elongated section of a normal-faulting system. A huge amount of seismic data has been collected by permanent and temporary seismic stations since the onset of the sequence.
About 230,000 seismic events have been analyzed to retrieve P and S seismic waves arrival times, which allowed us to compute 3-D velocity structure and precise earthquake locations.
For all of the earthquakes that meet strict selection criteria based on the signal to noise ratio, we computed the low frequency spectral level and the decay of the amplitude spectra (t*) of both P- and S-waves at about 150 recording sites. In order to avoid source complexity, we selected only events with M<2 for which the source corner frequency is beyond the analysed frequency band (1-40 Hz) and the spectral decay could be modeled only by attenuation effects. A preliminary fit of the observed spectra was used to compute the amplitude residuals between the observed and modeled spectra for P- and S- waves. For each station, the mean of the overall amplitude residuals, for each frequency, contribute to define the site response, a sort of site transfer function that is used to correct the observed spectra in a second round of fit. The high-frequency spectral decays (t*) are then computed again on the corrected spectra and they are used as input for tomography.
The applied method is a powerful tool to image the elastic properties of the medium in terms of seismic energy absorption, i.e. lower or higher attenuation of seismic waves. The retrieved pattern of attenuation gives useful insights on the physical state of the rocks in the crustal volume hosting the ruptured faults during the ongoing seismic sequence.
How to cite: De Gori, P., Lucente, F. P., Attolico, A., and Chiarabba, C.: Attenuation P-S-waves tomography of the Amatrice-Norcia fault system from high densely recorded aftershock data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10045, https://doi.org/10.5194/egusphere-egu25-10045, 2025.
In volcanic areas, seismic attenuation is greatly influenced by the presence of hot rocks and magma. This makes the spatial distribution of attenuation highly inhomogeneous and three-dimensional. The attenuation model can be expressed in terms of the attenuation coefficient α or the quality factor Q, both of which depend on the frequency of seismic waves. Hot rocks and magma affect especially S-wave propagation very strongly. In addition to attenuation, the S-wave velocity and the ratio of P-wave and S-wave velocities also change significantly.
To find the relationship between seismic S-wave attenuation and S-wave velocity, we studied the Reykjanes Peninsula region in SW Iceland, where intense volcanic activity has been ongoing since 2019. This area is monitored by the local seismic network REYKJANET, which consists of 17 stations. We have used 8602 seismic rays that link 680 earthquake foci to the Reykjanet stations. We determined the average value of the α and Q attenuation parameters as a function of frequency. We also determined the average seismic velocities vp and vs along these rays. We calculated the correlation between attenuation and seismic velocities. It turns out that there is a statistically significant dependence between these parameters.
The findings can be used to map the occurrence of magma in the upper crust in volcanic regions and thus contribute to the prediction of volcanic eruptions.
How to cite: Malek, J. and Fojtikova, L.: Correlation between seismic attenuation and S-wave velocity in the volcanic region of Reykjanes, Iceland, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5672, https://doi.org/10.5194/egusphere-egu25-5672, 2025.
In recent years, 3D seismic velocity models of the southern Apennines–Calabrian Arc border region have improved the definition of crustal structures at the northern edge of the Ionian subduction zone (see, e.g., Totaro et al., JoG, 2014). In this sector, a seismic gap, supported by the absence of major earthquakes in historical catalogues (https://emidius.mi.ingv.it/CPTI15-DBMI15/), was previously hypothesized by paleoseismological evidence (Cinti et al., SRL, 2015). In the upper crust, a low-velocity anomaly of both P- and S-waves was detected between the Calabrian and southern Apennines domains, characterized by higher velocities (Totaro et al., JoG, 2014). The low velocity- anomaly may be related to fluid rising along several SW-NE-oriented faults crossing Italy from the Tyrrhenian to the Ionian coasts (Minissale et al., Earth-Sci Rev, 2019). Seismic-wave attenuation is highly sensitive to fluid storage within geological structures. When scattering attenuation and absorption, the two primary attenuation mechanisms, are separated and mapped in space and time, they can constrain fluid migrations through tectonic structures (Reiss et al., GRL, 2022; Gabrielli et al., GRL 2023). For this study, we collected 3690 waveforms from 112 earthquakes (M≥3.0, hypocentral depth≤20km) that occurred in the area between September 2004 and October 2024. We used the MuRAT3.0 suite (De Siena et al., JVGR, 2014; Napolitano et al., SR, 2024) to map proxies of scattering attenuation and absorption (peak-delay times and late-time coda attenuation) in space. The results mark the presence of high-attenuation anomalies, potentially associated with sources of geothermal energy comprised in the low-velocity anomaly described by Totaro et al. (JoG, 2014). Seismic attenuation models provide complementary information to velocity tomography on the area's complex 3D structure. The results are jointly interpreted with those coming from geophysical and geological investigations (e.g., Totaro et al., BSSA, 2015; Brozzetti et al., JStructGeol, 2017; De Ritis et al., Tectonics, 2019), fully characterizing the crustal structure of the study area.
How to cite: Adam Alddoum Adam, M., De Siena, L., Presti, D., Scolaro, S., and Totaro, C.: Seismic attenuation tomography: new insights into fluid dynamics in the Northern Calabrian region (Italy) , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-871, https://doi.org/10.5194/egusphere-egu25-871, 2025.
In addition to the more common elastic crustal imaging, the investigation of attenuation properties is a pivotal task for gaining insights into the geological complexities of a study area. Indeed, the availability of scattering and absorption crustal images may allow for defining the extension of both highly fractured regions in seismogenic volumes and the presence of fluids, along with their possible role in the seismic activity of the target areas. Furthermore, the possible imaging of fluid saturated rock volumes could be a significant clue about the geothermal potential of target areas.
Our study is placed in this scientific framework, thus providing an unprecedented complete attenuation image of the High Agri Valley (HAV, Southern Italy). The latter is a NW-SE elongated basin located in southern Apennines, hosting the largest onshore oil field in Western Europe. Hydrocarbons are not the only fluids of interest in the area, as a meaningful amount of sulphureous hypothermal water and gases have been found in the Tramutola site, on the western side of the valley.
The HAV is bordered by two oppositely dipping fault systems: the Eastern Agri Fault System (EAFS) to the east, and the Monti della Maddalena Fault System (MMFS) to the west. In the area, one of the strongest earthquakes in Italy occurred (the 1857 Mw 7.0 earthquake) making the High Agri Valley a region affected by a very high seismic hazard. Furthermore, in the region there is a well-documented induced seismicity due to: 1) the combined effects of the water level oscillations of the Pertusillo lake, the regional tectonics, and likely the poroelastic/elastic stress due to aquifers in the carbonate rocks; 2) the injection, through the Costa Molina 2 well, of the wastewater produced by the exploitation of the Agri Valley oilfield.
The dataset adopted for our aims consists in the seismic signals recorded in the period 2016 – 2019 by a virtual network composed of the seismic stations belonging to INGV, ENI, and INSIEME seismic networks (Stabile et al., 2020). A total number of 650 earthquakes were recorded, with hypocentral depths ranging from 0 down to 10 km. The scattering and absorption imaging were retrieved by adopting an approach combining peak delay and coda-Q methodologies, already implemented in the open source code MuRAT (De Siena et al., 2016). The preliminary results show high scattering and high absorption at depth between 2 and 3.5 km featuring Costa Molina 2 injection well location, in agreement with the interpretation of a volume fractured by high-pressure injected fluids. Other high intrinsic attenuation anomalies have been found at similar depths in the Tramutola and Pertusillo Lake areas, while a deeper strong absorption has been found in the northern HAV at greater depth (4.5 km).
How to cite: Serlenga, V., Napolitano, F., Amoroso, O., Giampaolo, V., Stabile, T. A., De Siena, L., and Capuano, P.: Attenuation imaging of the High Agri Valley (Southern Italy) revealed by peak delay and coda Q analysis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12024, https://doi.org/10.5194/egusphere-egu25-12024, 2025.
On February 6th, 2023, an earthquake of Mw 7.8, known as the Kahramanmaraş earthquake, struck between southern Turkey and northern Syria. The strike-slip event ruptured multiple southwestern segments of the East Anatolian Fault System (EAFS). It was followed by a severe series of aftershocks, as the Mw 7.6 Elbistan earthquake, occurred just nine hours from the Kahramanmaraş event, rupturing an east-west trending fault near the main EAFS. The Mw 6.4 Antakya aftershock occurred along a bifurcation of the EAFS.
Seismic attenuation is a powerful tool to look at variations in the crustal properties, being strongly controlled by structural irregularity and heterogeneities: fractures, temperature, and pressure variations can cause an increase or a decrease in the amplitude of seismic wave amplitude. Hence, seismic attenuation imagining can provide us with information about the areas with a variation in fracturing or other changes in the crust (Gabrielli et al., 2022; 2023; 2024).
This work aims to present an initial 3D imaging of seismic wave scattering variations before and after the February 6th earthquakes, examining their spatial and temporal changes at different frequency bands. To achieve this, we utilized distinct datasets: the first covers the period before the sequence (pre-sequence phase, January 2020 - February 5, 2023), while the second begins with the February 6 event and extends through May 2023 (sequence phase). The datasets are composed of ~48000 waveforms for the pre-sequence and ~238000 for the sequence, recorded by 64 stations, ensuring a good coverage for our analysis in the examined area.
We calculated the peak-delay parameter, a proxy of seismic scattering, and mapped using a regionalization approach. The preliminary results show a difference between the pre-sequence and the sequence phase, with increased scattering between the EAF main branch and the Sürgü-Çardak Fault (to the northwest). Between the EAF and the North Anatolian Fault/Bingol area, we record a constant high scattering.
How to cite: Gabrielli, S., Akinci, A., Zhou, Y., Del Pezzo, E., and De Siena, L.: 3D Analysis of Scattering Attenuation Before and After the February 6, 2023, Earthquake Doublet in Türkiye, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11209, https://doi.org/10.5194/egusphere-egu25-11209, 2025.
Seismic attenuation tomography is a valuable geophysical method for imaging complex geological assessments at local and regional scales. It effectively detects melt, fractures, and strain conditions in rocks, and its reliability has been confirmed through laboratory experiments.
This study focuses on locating the Collalto underground gas storage (UGS) in the eastern Southern Alps of Northern Italy through seismic attenuation tomography. It represents the first multiscale attenuation imaging of the Montello thrust, which belongs to the segment of the Alpine boundary thrust covering about 100 km from Vicenza to Pordenone. The region faces medium to high seismic hazards, monitored by a local seismic network managed by the National Institute of Oceanography and Applied Geophysics in Trieste.
Using data from this network and the Murat code, we analyzed scattering, absorption, and total attenuation, interpreting results alongside geological-structural data. Our models confirm the principal attitude of the Montello thrust system, also highlighting minor faults that distribute deformation and seismic activity.
At a local scale, the absorption model highlights the methane-rich volume (Collalto UGS) as notably attenuative, indicating the method's effectiveness in detecting fluids. It also reveals deeper attenuative patches that anti-correlate with seismicity, suggesting a deeper layer of fluids likely influencing tectonic behavior.
These results open the path for further interdisciplinary research to develop comprehensive seismotectonic models integrating seismic activity with rock properties and deformation patterns.
How to cite: Talone, D., Maria Adelaide, R., Luca, D. S., Mariangela, G., Marco, S., Laura, P., Giusy, L., and Rita, D. N.: Multi-scale attenuative imaging of the Collalto UGS area and the Montello thrust system (eastern Southern Alps, Italy), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6650, https://doi.org/10.5194/egusphere-egu25-6650, 2025.
Seismic attenuation has long been an important measurable property of rocks, valuable for eliminating path information from source models and understanding seismic hazards. Over the last 30 years, total attenuation and its two primary components—seismic scattering and absorption—have emerged as state-of-the-art tomographic attributes ranging from planets to the core, to the lithosphere, to rocks. Following the rise of seismic interferometry, stochastic seismic wavefields, once the exclusive domain of the “Heterogeneous Earth” community, have now become vital data for attenuation tomography in tectonic and volcanic settings.
Despite the importance of seismic tomography for Earth Sciences, few open-access codes combine the rigorous treatment of seismic data with novel tomographic tools in a collaborative environment. MuRAT has been a complete solution for seismic attenuation, scattering, and absorption imaging since 2014. It includes modules that provide coherent- and incoherent-wave forward models based on ray theory and radiative transfer equations that seismologists can define using simple SAC files. Fully coded in Matlab©, it links to community-wide inversion packages and is thought of as a fully cooperative environment based on GitHub. The package has been applied to all crustal scales, from stable continental regions to hundreds-meter- active surveys in volcanic areas.
MuRAT3 (https://github.com/LucaDeSiena/MuRAT) is the first full 3D release of this code. It is specifically designed to integrate state-of-the-art forward-modelling tools from seismology to push current frequency and scale boundaries in seismic attenuation imaging. Here, I will present the last benchmark in attenuation imaging, illustrating how the code works, its success stories, its limitations, and the direction to follow to mitigate them.
How to cite: De Siena, L. and the MuRAT Team: MuRAT3: A new generation of Multi-ResolutionAttenuation Tomography., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1937, https://doi.org/10.5194/egusphere-egu25-1937, 2025.
The Central Anatolian Plateau, featuring its volcanic provinces, is a significant transition zone that marks the abrupt shift from continental collision and compressional deformation in the east to oceanic subduction and extensional dynamics in the west. A comprehensive understanding of physical properties, including seismic attenuation within the crust, can illuminate the potential causes of geodynamic processes and related volcanic activity. Here, we analyse S-wave attenuation and peak delay using data from the Continental Dynamics–Central Anatolian Tectonics (CD-CAT) seismic deployment conducted between 2013 and 2015. Strong attenuation is observed in the Cappadocia volcanic region, indicating active magmatic systems, thermal anomalies, and fluid-rich regions. The anomaly body shows a NE-SW trend consistent with volcanic group distribution, indicating that the regional tectonic stress field controls magmatic activity from east to west. The anomaly body's depth gradually decreases from 12 km to 5 km, possibly revealing the geometry of shallow magmatic storage systems. Peak delay time shows positive anomalies in the volcanic region, indicating highly fractured crustal rocks, whereas negative anomalies in the subduction front region reflect dense ones. The deep magmatic system shows directional characteristics consistent with plate kinematic observations. The unique distribution of anomaly depth gradually decreasing from NE-SW may reveal the existence of shallow magmatic storage systems, with this depth range possibly representing the location of main magma chambers and the vertical extent of magmatic conduits.
This research is supported by the National Natural Science Foundation of China (U2139206, 41974061, 41974054) and the Special Fund of China Seismic Experimental Site (2019CSES0103). The first author has also been financially supported by the China Scholarship Council (202204910302).
How to cite: Zhu, W.-M., De Siena, L., Zhao, L.-F., Eken, T., Xie, X.-B., and Yao, Z.-X.: Shallow magmatic storage systems linking to main magma chambers beneath the Central Anatolian Plateau, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21444, https://doi.org/10.5194/egusphere-egu25-21444, 2025.
Our study introduces Sn wave attenuation tomography model developed for the eastern Nepal Himalaya. The objective is to explore the complex upper mantle heterogeneity beneath this tectonically significant region. Employing a robust network comprising 155 seismic stations (operational under XF, XQ, and YL networks), we have carefully analyzed 113 regional seismic events captured through 3433 seismic waveforms. The interstation Q values were calculated utilizing the Two Station Method (TSM). Following this, the least‐squares orthogonal factor decomposition (LSQR) inversion technique was used to develop a detailed tomographic model for this region, illustrating the spatial variations in Sn wave quality factor (Sn Q) across the region. Our results revealed a prevalence of low Q values, ranging from 20 to 100 throughout the area. The central region of our study exhibits medium Q value ranging from around 100 to 300. Moreover, isolated pockets of exceptionally high Q values have been observed in the northwestern and southeastern parts of the region. The tomographic results of this study are in sync with previously reported high attenuation in and around this region. This study enhances our understanding of the upper mantle beneath the eastern Nepal Himalaya, providing valuable insights into the lithospheric architecture and geodynamics of the region, as well as Sn wave propagation dynamics.
How to cite: Bose, S., Singh, C., and Singh, A.: Mapping Sn wave attenuation tomography across the Eastern Nepal Himalaya: Insights from Two Station Method, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14832, https://doi.org/10.5194/egusphere-egu25-14832, 2025.
Sikkim Himalaya is an actively deforming part of the Himalayan orogen which formed as a result of an impactful continental-continental collision. Recent studies have characterized the region by bimodal seismicity resulting from a dynamic multi-fault system against the backdrop of spatially varying geological and geophysical features. In this study, we attempt to map the distribution of crustal inhomogeneity beneath Sikkim Himalaya using peak delay time (Tpd) analysis of the S-wave envelope. Quantitative estimations at 6 Hz central frequency shows predominant path dependence (B > 0.5) suggesting strong multiple forward scattering due to presence of inhomogeneities. Further, we produced 3-D peak delay perturbation (ΔLog(Tpd)) map to investigate the depth distribution of inhomogeneities. Spatial variation maps at six distinct depths reveal high ΔLog(Tpd) between 0-15 km in the south, southwestern Sikkim, and eastern Nepal region which elucidate the presence of a highly heterogeneous decollement surface along which the Indian plate is underthrusting beneath the Tibetan plateau. On the contrary, the shallow crust of northern Sikkim portrays negative ΔLog(Tpd) which evidences an undeformed medium, corroborated with the lack of seismicity at shallower depths. Investigation of the depth section along the southeast-northwest direction reveals a zone of highly deformed crust across MHT with prevalent micro-seismic activity. The said zone coincides with low S-wave velocity and low coda attenuation parameter which transpires to the presence of numerous inhomogeneities with the possible presence of fluid as well. We also observe deformation in the foothills of Himalaya possibly induced due to the upliftment of the Shillong plateau.
How to cite: Singh, C., Dutta, A., and Singh, A.: Discerning crustal deformation patterns beneath Sikkim Himalaya, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6331, https://doi.org/10.5194/egusphere-egu25-6331, 2025.
The Alaskan mainland overlies the subducting Pacific plate and Yakutat microplate as they subduct beneath the southern margin of the North American plate. South-central Alaska features massive volcanoes of different types, including intraplate volcanoes, Aleutian arc volcanoes, and a group of densely clustered volcanoes called the Wrangell volcanic field (WVF). How the Denali volcanic gap (DVG) formed and why the Wrangell volcanoes are clustered remain vigorously debated. Investigating the crustal thermal structure can be crucial for understanding subsurface magmatic activity. Seismic attenuation, or the quality factor Q, usually provides good constraints on the viscoelastic structure and is sensitive to thermodynamic processes in the lithosphere, such as partial melting and high-temperature magmatism. Regional Lg-waves propagating in the continental crust waveguide are an ideal phase for investigating crustal attenuation. In this study, based on vertical-component waveform data recorded by 20 permanent and temporary seismic networks in Alaska, we established a high-resolution broadband crustal Lg-wave attenuation model for Alaska and nearby regions. Strong Lg attenuation is observed beneath the volcanoes in south-central Alaska, indicating thermal anomalies and possible melting in the crust. In contrast, the central Yakutat terrane and DVG are characterized by weak Lg attenuation, suggesting the existence of a cool crust that prevents hot mantle materials from invading the crust. This cool crust is likely the reason for the DVG. Quarter-toroidal crustal melting with strong attenuation is revealed around the Yakutat terrane. This curved zone of crustal melting, possibly driven by toroidal mantle flow, weakly connects the Wrangell and Buzzard Creek-Jumbo Dome magmatic chambers.
This research was supported by the National Natural Science Foundation of China (42430306 and 42404067), the China Postdoctoral Science Foundation (2024M751295) and the Postdoctoral Fellowship Program of CPSF (GZC20240638).
How to cite: Yang, G., Zhao, L.-F., Xie, X.-B., He, X., Zhang, L., and Yao, Z.-X.: Lg-wave attenuation tomography in the Alaskan mainland: Implications for the formation of volcanic gap and clustered volcanism, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-193, https://doi.org/10.5194/egusphere-egu25-193, 2025.
A typical triple junction in Colombia is critical for understanding the plate convergence and coupling among the South American plate and the subducting Nazca and Caribbean plates (González et al., 2023). However, locating this triple junction is challenging due to the complex geodynamic evolution and uncertainty in the plate boundaries. Magmatic arc activity has been diverse and discontinuous due to varying subduction angles, resulting in blocks with distinct rheological properties and thermal structures (Lagardère and Vargas, 2021). Seismic Lg waves are a prominent phase in high-frequency regional seismograms (e.g., Gutenberg). Compared with velocity data, seismic wave attenuation is more sensitive to deep materials' temperature and rheological strength (Boyd et al., 2004; Zhao et al., 2013). Therefore, we developed a high-resolution Lg-wave attenuation model for Colombia and surrounding areas to constrain crustal magmatic activity, linking deep dynamic processes with surface volcanism and determining potential plate boundaries at the crustal scale. The ancient and stable Guinan Shield is characterized by weak Lg attenuation. In contrast, the area encompassing Central America, western Colombia, and Ecuador features strong Lg attenuation and concentrated volcanoes, indicating thermal anomalies or partial melting in the crust. Low QLg is shown near the Caldas tear along 5.5°N, speculating that a hydrothermal uplift channel caused by the Nazca plate tear may exist at depth. Based on our results and other geological and geophysical data, the thermal distribution due to the subduction of the Nazca and Caribbean plates suggests that the boundary between the subducting Nazca and Caribbean slabs beneath the South American plate may be located at 7.5°N, and that the potential location of the triple junction may be located at 7.5°N, 77°W. This research was supported by the National Natural Science Foundation of China (U2139206, 41974061, 41974054).
References
Boyd, O. S., Jones, C. H., & Sheehan, A. F. (2004). Foundering Lithosphere Imaged Beneath the Southern Sierra Nevada, California, USA. Science, 305(5684), 660–662.
Hey, R., 1977. Tectonic evolution of the Cocos-Nazca spreading center. Geol. Soc. Am. Bull. 88, 1404.
González, R., Oncken, O., Faccenna, C., Le Breton, E., Bezada, M., Mora, A., 2023. Kinematics and Convergent Tectonics of the Northwestern South American Plate During the Cenozoic. Geochem. Geophys. Geosystems 24, e2022GC010827.
Lagardère, C., Vargas, C.A., 2021. Earthquake distribution and lithospheric rheology beneath the Northwestern Andes, Colombia. Geod. Geodyn. 12, 1–10.
Kellogg, J.N., Vega, V., Stailings, T.C., Aiken, C.L.V., Kellogg, J.N., 1995. Tectonic development of Panama, Costa Rica, and the Colombian Andes: Constraints from Global Positioning System geodetic studies and gravity, in: Geological Society of America Special Papers. Geological Society of America, pp. 75–90.
Vargas, C.A., Ochoa, L.H., Caneva, A., 2019. Estimation of the thermal structure beneath the volcanic arc of the northern Andes by coda wave attenuation tomography. Front. Earth Sci. 7, 208.
Zhao, L.-F., Xie, X.-B., He, J.-K., Tian, X., & Yao, Z.-X. (2013). Crustal flow pattern beneath the Tibetan Plateau constrained by regional Lg-wave Q tomography. Earth and Planetary Science Letters, 383, 113–122.
How to cite: Tian, B., Liu, Z., Zhao, L.-F., Xie, X.-B., Vargas, C. A., and Yao, Z.-X.: High-resolution Lg attenuation structure of the Colombian crust and its implications for the volcanic mechanism and plate boundary, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3917, https://doi.org/10.5194/egusphere-egu25-3917, 2025.
The eastern margin of the Tibetan Plateau is an area with the youngest uplift, strongest deformation, and frequent occurrence of large earthquakes. Seismic velocity can constrain the lithosphere's rheological strength and crustal flow distribution, allowing the deformation to be explored for the crust and upper mantle. However, seismic velocity is related to rock strength and composition and reflects the rock's elastic behavior. As a direct anelastic observation of deep temperature and rheological strength, seismic attenuation can decrease the multiplicity of geodynamic interpretation. We construct a broadband high-resolution attenuation model for the lithosphere in the eastern margin of the Tibetan Plateau by using regional seismic phases propagating in the crust and uppermost mantle. A rheological strength structure was obtained from a seismic attenuation model of the lithosphere. The dynamic origins of the distribution of soft, ductile materials can be investigated. Hence, the tectonic evolution and seismogenic environment under the lithospheric compression and collision can be detected in the eastern margin of the Tibetan Plateau. This research was supported by the National Natural Science Foundation of China (U2139206).
How to cite: Zhao, L.-F., Xie, X.-B., He, X., Li, R.-J., Chang, X., and Yao, Z.-X.: Seismic Q model and lithosphere rheology in the eastern margin of the Tibetan Plateau, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2326, https://doi.org/10.5194/egusphere-egu25-2326, 2025.
