The challenge of modeling site effects in complex geological environments remains a central topic in engineering seismology and is the focus of this session.
Addressing this issue begins with identifying "complex" sites where simple prediction models, based on 1D velocity profiles, fail to provide satisfactory results. This requires comparing actual site effects with predictions from physical models across large datasets. Recent advances now enable such analyses, thanks to the quantification of site effects through generalized inversion methods or spectral ratio calculations between deep and surface stations in regions equipped with borehole networks. Systematic tests using extensive data from Japan’s Kik-net and K-NET networks reveal that a significant proportion of sites deviate from 1D behavior, particularly at frequencies above 3 Hz.
To meet this challenge, we propose three complementary approaches to improve site effect predictions for complex environments:
- Enhanced High-Frequency Physical Modeling: Improving and calibrating attenuation models is essential and feasible, paving the way for more accurate high-frequency predictions.
- Increased Observation Density: Expanding observational coverage in urban areas through innovative methods, such as leveraging smartphone data, can significantly enhance datasets and support the development of high-resolution amplification maps.
- Machine Learning Applications: Developing machine learning models tailored to available site information—ranging from geological and geotechnical data to recorded seismic data—offers a flexible, novel, and testable framework for site effect prediction.
This presentation will discuss the methodologies and results of recent studies, highlighting how these strategies can advance our understanding and modeling of site effects in complex geological settings.
How to cite: Cotton, F., Bossu, R., Finazzi, F., Pilz, M., and Zhu, C.: Predicting Site Effects on "Complex" Geological Sites in the Era of Big Data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8664, https://doi.org/10.5194/egusphere-egu25-8664, 2025.
Earthquakes pose a significant threat worldwide, requiring rapid and accurate damage assessments to guide emergency response efforts. While empirical ground motion models are commonly used for their speed and simplicity, they often fail to account for critical factors such as site effects and the spatial variability of ground shaking. Physics-based ground shaking simulations can provide a more accurate alternative by modelling fault rupture, wave propagation and local site effects. However, their application in the near real-time has been limited due to computational complexity and long processing times. To overcome these limitations, we have developed UrgentShake, an HPC-based system designed to generate physics-based ground shaking scenarios under strict time constraints. A key focus of UrgentShake is the implementation of efficient strategies to reduce the computational time required to produce reliable solutions without compromising accuracy. Preliminary evaluations on two reference seismic events demonstrate UrgentShake's capability to significantly reduce time-to-solution, ensuring its potential to meet the critical timing demands of seismic emergency responses.
How to cite: Zuccolo, E., Bolzon, G., Pitari, F., Rodríguez Muñoz, L., Monsalvo Franco, I. E., Scaini, C., Poggi, V., Smerzini, C., and Salon, S.: UrgentShake: An HPC System for Near Real-Time Physics-Based Ground Shaking Simulations to Support Emergency Response Efforts , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9353, https://doi.org/10.5194/egusphere-egu25-9353, 2025.
Physics-based numerical simulations of seismic ground motion are crucial for advancing our understanding of regional earthquake hazard and risk. Complex geometries in sedimentary basins, coupled with strong surface topography, can cause significant variations in ground motion. To model these effects, a 3D representation of surface topography and available 3D models of the sedimentary basin velocity structure are used in numerical simulations. Using the spectral-element method, we synthesise displacement, velocity and acceleration waveforms in the Rhône valley, Switzerland. This region is characterized by complex topography, morphology, and significant seismic hazard.
We perform spectral-element waveform simulations with a maximum resolvable frequency of 5 Hz to investigate the joint effects of 3D basin structure and surface topography on ground shaking. Moderate-magnitude earthquakes that have been recorded in the area are used as point sources. Additionally, we compute waveforms for scenario earthquakes taken from the disaggregation of the current Swiss hazard model, SUIhaz2015 (Wiemer et al., 2016).
Our goal is to assess how these factors affect amplification patterns in different basin parts and topographic areas. We do so by comparing ground motion peak values at different altitudes (on mountains and valley floors with soft sediment conditions). Additionally, we calculate engineering-relevant ground motion parameters, such as cumulative velocity and significant duration up to the resolved frequencies, that help improve hazard estimations in the Rhône valley.
With our study, we show that the joint effects of topography and basin structure lead to larger amplification variations within the basin, and in the surrounding reliefs. We conclude that physics-based simulations have the potential to provide an adequate alternative for input ground motion in seismic hazard analysis. This is particularly relevant for modelling hypothesized earthquakes, which are essential for the assessment of seismic hazard in areas facilitating crucial infrastructure.
How to cite: Koroni, M., Ermert, L. A., Bergamo, P., and Fäh, D.: Physics-based modelling of ground motion in alpine valleys including strong surface topography and 3-D basin structure: A case study of the Rhône valley (CH), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5638, https://doi.org/10.5194/egusphere-egu25-5638, 2025.
Understanding the complexity of earthquake source parameters, including coseismic slip distribution and rupture dimensions, is essential for local-scale seismic and tsunami hazard assessments. One effective approach is to use earthquake source models generated from synthetic earthquake catalogues via physics-based generators like RSQSim. A key factor influencing the characteristics of a synthetic earthquake catalogue is the tectonic stressing rate, calculated from the slip-deficit rate using a back-slip loading method. The slip-deficit rate can be calculated by integrating the geodetically-inferred convergence rate from Euler Pole rotations with seismic coupling models. Unfortunately, some of the world’s subduction zones have insufficient geodetic data to significantly constrain coupling models. Such is the case with our focus area in the southwest Pacific. To overcome this challenge, we estimate coupling factors on subduction interfaces by adjusting them according to the seismicity rate ratios between the instrumental and synthetic earthquake catalogues of the baseline models. The subduction interfaces are divided into several segments for calculating the seismicity rate ratios along strike. To incorporate sufficient instrumental earthquakes for seismicity rate estimates and to avoid artificial segmentation, we test the segment window lengths and shifting distance. Our new method is applied to the Tonga and Vanuatu subduction zones, which exhibit the highest convergence rates among subduction zones worldwide of approximately 240 mm/year. The coupling factor in this area was poorly defined in previous studies, leading to debate about whether the coupling was weak or strong in each segment. The ideal coupling distribution occurs when adjusted by seismicity rate ratios calculated with a 500 km moving window shifted 50 km along the strike for the Tonga and Vanuatu subduction zones. The results show weak coupling at northern Tonga and strong coupling at northern Vanuatu interfaces. We use this model to develop a synthetic catalogue of finite fault earthquakes spanning ~60,000 years.
How to cite: Liao, Y.-W. M., Fry, B., Williams, C., Howell, A., and Nicol, A.: Earthquake source modelling for hazard assessment of the Tonga and Vanuatu subduction zones , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3979, https://doi.org/10.5194/egusphere-egu25-3979, 2025.
Accurate modeling of earthquake ground motions is critical for understanding rupture dynamics and assessing seismic hazard. However, traditional models that employ simple, smooth dynamic rupture representations often struggle to capture ground motion beyond the corner frequency. This limitation stems from their inability to account for the high-frequency content generated by small-scale complexities in the rupture process, leading to underestimation of the spectral content observed in real earthquake recordings. Here we investigate dynamic rupture models incorporating broadband spatial variability in dynamic rupture parameters. Our study implements a multi-scale heterogeneity approach based on the Von Karman autocorrelation function with power spectral density of k-2 (Hurst exponent of zero) and correlation lengths that scale with the rupture size. We thereby introduce variations in initial stress, fault strength, and characteristic slip weakening distance across the fault plane. The degree of rupture complexity in our simulations is effectively controlled by the standard deviation of the imposed heterogeneities. We demonstrate the effectiveness of our approach by modeling the apparent source spectra of two Mw~4 events from central Italy up to 25 Hz. The first is a unilateral event showing a strong azimuthal dependence of spectral amplitudes due to directivity effects, while the second is a non-directive bilateral event exhibiting a more homogeneous distribution. By comparing synthetic and observed apparent source spectra, we show how our approach successfully models these two contrasting rupture processes. Furthermore, comparison with the theoretical ω-2 model provides additional insights into the relationship between source complexity and source spectral characteristics. The dynamic rupture heterogeneities prove crucial for reproducing the high-frequency ground motion components that simple models typically fail to capture. This work represents a significant step forward in bridging the gap between earthquake recordings and numerical modeling, providing a robust framework for understanding and predicting ground motions applicable in earthquake scenario simulations.
How to cite: Joshi, L. and Gallovič, F.: Heterogeneity in Dynamic Rupture Models: Bridging the Gap Between Observed High-Frequency Ground Motion and Rupture Process Complexity, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5717, https://doi.org/10.5194/egusphere-egu25-5717, 2025.
Earthquakes are commonly associated with brittle failure and frictional sliding in the uppermost 70 km of the Earth. Yet, a significant fraction of seismic events are detected at depths of up to 700 km (deep earthquakes). As these events are difficult to reconcile with our understanding of brittle failure, they are likely facilitated by a ductile weakening mechanism instead. Thermal runaway describes the positive feedback loop of shear heating, temperature-dependent viscosity and deformation. This mechanism has been proposed as a driver of deep earthquakes, and several one-dimensional (1D) studies support its viability. However, two-dimensional (2D) models that show the transient propagation of highly localized shear zones due to thermal runaway are still missing.
We present 2D thermomechanical models which employ a composite visco-elastic rheology, combining elasticity with diffusion creep, dislocation creep and low-temperature plasticity. The code is written in the Julia programming language, operates on Graphic Processing Units (GPU) and utilizes the pseudo-transient relaxation method. Our models capture the nucleation of ductile ruptures on small perturbations, and their transient propagation through a previously intact host rock. Slip velocities inside the ductile ruptures are initially on the order of the far-field deformation, but as the rupture self-localizes, velocities quickly increase by several orders of magnitudes and reach the range of earthquakes (> 1 mm s-1). The ductile ruptures propagate parallel to the simple-shear background deformation without pre-existing faults or weak layers. If multiple perturbations are present, thermal runaway may nucleate in multiple locations and ruptures can bend to connect to each other.
The magnitude of maximum slip velocity strongly depends on the ratio of stored elastic energy to thermal energy when deformation transitions from low-temperature plasticity to diffusion or dislocation creep. This ratio is derived from one-dimensional models but retains its validity in 2D. If it is small (e.g., low stress, high temperature), shear zones are broad, and deformation is slow. For medium values, slip velocities are in the range of aseismic slow slip events (SSEs). For large energy ratios (e.g., high stress, low temperature), slip velocities reach the seismic window.
Such high-stress conditions are most likely to occur in the cold cores of subducting slabs when they approach the bottom of the mantle transition zone. The resistance of the lower mantle causes slabs to deform, and the large overburden pressure increases viscosity. Both effects increase stress levels. This depth also coincides with the highest occurrence rate of deep-focus earthquakes.
How to cite: Spang, A., Thielmann, M., de Montserrat, A., and Duretz, T.: 2D numerical models of ductile rupture propagation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4156, https://doi.org/10.5194/egusphere-egu25-4156, 2025.
The rise in frequency and magnitude of anthropogenic earthquakes has raised public concern and underscored the importance of understanding subsurface processes and mechanisms to assess induced seismic hazards and risks. While faults are ubiquitously rough, and the characteristics of fault roughness are well investigated and constrained by natural observations, the interplay between roughness and successive rupture events in induced seismicity remains poorly understood. Here, we simulate seismicity induced by fluid injection on a self-affine rough fault. The model assumes instantaneous weakening from static to dynamic friction, homogeneous friction coefficients, and instantaneous frictional healing after each earthquake. We investigate how pore pressure diffusion, initial stress state, and fault roughness influence the stress distribution and the seismicity front. We find that fault roughness significantly alters the statistical distribution of distance to failure (critical pressure), transitioning from an approximately normal distribution at low roughness to a highly skewed distribution at high roughness. Furthermore, models with similar initial stress distributions have comparable seismic fronts, highlighting the critical influence of pre-existing stress conditions. With additional simplifications, the seismicity front and back-front can be predicted reasonably well based on the initial stress distribution and the spatio-temporal evolution of pore pressure. This provides a basis for understanding additional factors such as stress interactions and spatial correlation that influence the seismicity front.
How to cite: Lin, H.-F., Candela, T., and Ampuero, J.-P.: Seismicity front induced by fluid injection on rough faults, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2294, https://doi.org/10.5194/egusphere-egu25-2294, 2025.
Stress-drop is the overall reduction of average stress due to energy release during an earthquake, and should reflect geometrical, rheological and dynamic properties of the seismic source. Stress-drop values, estimated using seismological data, vary over four orders of magnitudes making the stress-drop an enigmatic parameter. There have been many efforts to reduce the stress-drop scatter, and to perceive better understanding of the factors controlling its variability. These efforts focused mainly on observational aspects, in which source properties such as, corner-frequency and seismic moment, were measured, considering site, path and additional source properties. Standard cubic power-law relation between corner-frequency of radiated waves and stress-drop, with a constant coefficient K, is and additional reason to its significant scatter. We provide a new formulation, applying a strain-drop dependent K; by that leading to a significant reduction of the relation of stress-drop to corner-frequency, down to a power-law of 3/4. Results based on a wide range of theoretical, laboratory and observational measurements demonstrate that the new formulation significantly narrows the three to four orders of magnitude of scatter, to about one order of magnitude around a value of 10MPa. The more converged range of stress-drop values, obtained by the suggested new formulation, may be used to support those who argue for self-similarity of earthquakes. In summary, the impact of the uncertainties of the source properties, seismic moment, M0, seismic potency, P0, and corner frequency, fC, on the value of stress-drop is not as dramatic as so many studies argued before. Furthermore, as we demonstrate, the reduction of scatter does not eliminate internal trends, controlled by geometrical, rheological and dynamical properties at the source.
How to cite: Kurzon, I., Lyakhovsky, V., and Sagy, A.: New formulation reduces the scatter of earthquake stress drop estimation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3345, https://doi.org/10.5194/egusphere-egu25-3345, 2025.
One of the key challenges of empirical ground-motion models is the ability to capture ground-motion variability, which may stem from different source, path and site effects. This challenge may be addressed using simulated data from physics-based, non-ergodic earthquake simulations. Dynamic rupture models capture the nonlinear interaction of source, path and site effects in a self-consistent way and once integrated with observations, reproduce a variety of geodetic and seismic data well to first order (e.g., Taufiqurrahman et al., 2022; Jia et al., 2023; Gabriel et al., 2023). However, these models may not fully account for the variability in ground motions, particularly in the orientation, periods (Tp), and amplitudes of long-period pulses (Yen et al., 2024). In addition, the physical mechanisms underlying high-frequency radiation remain debated (Graves & Pitarka, 2016; Ben-Zion et al., 2024).
In this study, we investigate the effects of incorporating both on-fault and structural small-scale heterogeneities within 3D dynamic rupture models of the 2023 Turkey earthquake doublet. Specifically, we focus on how these heterogeneities influence rupture dynamics, together with the spectral content and variability of the modelled ground motions. We analyse the impact of small- and large-scale fractal on-fault roughness, a heterogeneous distribution of fracture energy (Dc) and the dynamic friction coefficient (𝜇d), and initial supershear rupture speed compared to sub-shear earthquake initiation.
Our findings reveal that rupture dynamics are most significantly influenced by the introduction of an initial supershear rupture speed, which results in an expected larger seismic moment along the nucleating Nurdaği-Pazarcik splay fault and an earlier triggering of the East Anatolian Fault (EAF) compared to the other models. Although this leads to a greater overall energy release, the release pattern along the EAF remains fairly consistent across all models, suggesting that the added ingredients primarily act to amplify seismic moment rather than drastically alter rupture dynamics. Additionally, Dc heterogeneities have the most significant influence on long-period pulse properties. In contrast, small-scale roughness and 𝜇d heterogeneities exhibit a damping effect on pulse period (Tp) as they mostly influence high-frequency radiation. However, these modifications fail to translate into significant changes in the overall spectral content across the different models. Notably, despite the added heterogeneities, the pulse orientations remain predominantly fault normal and are only minimally impacted by Dc heterogeneities, supershear rupture speeds, and large-scale roughness.
This study demonstrates that incorporating a heterogeneous distribution of fracture energy has one of the strongest impacts on both the rupture dynamics and frequency content of 3D dynamic rupture simulations, further contributing to a better understanding of how different dynamic rupture heterogeneities influence ground shaking, a critical step towards comprehensively capturing ground-motion variability and enhancing physics-based seismic hazard assessment.
How to cite: Preca Trapani, R., Gabriel, A.-A., Marchandon, M., Ulrich, T., Wu, B., Yen, M.-H., and Cotton, F.: Do physics-based models improve predicted ground motion variability? Insights from dynamic rupture simulations of the 2023 Turkey Earthquake Sequence , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18476, https://doi.org/10.5194/egusphere-egu25-18476, 2025.
Recent improvements of large-scale ground motion simulations resulting from physics-based rupture and wave propagation models and accessible high-performance computing have made possible the potential use of synthetic ground motion in engineering applications. They provide scientists and engineers with new data that can yield new insight on the characteristics of ground motions and the variability of the infrastructure response. Such simulations can also make a significant contribution to the reduction of uncertainty in ground motion models (GMMs) that are being developed for large earthquakes at near-fault distances where ground motion variability is not fully captured by current sparsely recorded data.
An important aspect of the development and calibration of regional physics-based simulation platforms is the validation of their methodology and synthetic ground motion. Independent criteria that involve direct comparisons with recorded earthquakes, comparisons with exiting region-specific ground motion models for scenario earthquakes, and comparison with recorded buildings response should be requirements for trusted validation analysis.
In an effort to build confidence in simulated ground motion we compiled published results of validation analysis performed by several modeling teams and analyzed the general performance of their physics-based ground motion simulations. We focused on broad-band simulations that use a deterministic approach in computing ground motion time histories for crustal earthquakes. The analysis includes simulation results of selected recorded and scenario earthquakes with the magnitude ranging from 5.4 to 7.5. The goals of our study are to demonstrate that current physics-based kinematic rupture models can produce ground motions that agree with observed ones and empirical estimates, and that well-constrained reginal velocity models are capable of producing the expected wave scattering affecting ground motion variability and amplitude at local and regional distances. Satisfying these goals provides confidence in the predictive capabilities of the simulation platforms and the quality of synthetic ground motion in various engineering applications, including development of non-ergodic GMMs and building response analysis.
How to cite: Akinci, A. and Pitarka, A.: Performance of Physics-based Deterministic Ground Motion Simulations: Building Confidence in Using Broad-Band Synthetic Ground Motion in Engineering Applications, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7343, https://doi.org/10.5194/egusphere-egu25-7343, 2025.
The Korean Peninsula, located on the eastern margin of the Eurasian plate, has historically exhibited the low seismicity characteristic of intra-plate regions. However, the 2016 M 5.8 Gyeongju earthquake, the largest instrumentally recorded inland earthquake in the region, challenged the perception of the peninsula as a seismically safe zone. This event underscored the need for comprehensive seismic hazard assessment and mitigation strategies. Understanding ground motion characteristics of future large earthquakes is critical for advancing these efforts. Recently, physics-based broadband ground motion simulations using dynamic rupture models have gained popularity for studying near-source strong ground motion characteristics. In this study, I performed broadband (0.1–10.0 Hz) ground motion simulations of the 2016 Gyeongju earthquake using dynamic rupture modeling with the slip-weakening friction law on high-performance computing platforms. To enhance the heterogeneity of rupture processes and generate high-frequency (> 1 Hz) ground motions, I incorporated heterogeneity in the slip-weakening distance, modeled using the von Karman distribution. The distribution was controlled by three key input parameters: correlation length, Hurst exponent, and standard deviation. Preliminary results indicate that incorporating heterogeneous slip-weakening distances produces higher-frequency ground motions compared to homogeneous models. However, the simulated high-frequency energy remains insufficient to match the observed data fully. This highlights the importance of further refining physics-based broadband ground motion simulation methods to support advanced seismic hazard assessments. Future work will explore a broader parameter space for the heterogeneity of dynamic rupture parameters, including stress drop, strength excess, and slip-weakening distance. Additionally, the developed dynamic rupture models could be used to derive pseudo-dynamic rupture models, leveraging the source statistics of key kinematic parameters. These efforts aim to establish a robust physics-based broadband ground motion simulation platform for improved seismic hazard evaluation.
How to cite: Song, S. G.: Physics-based broadband ground motion simulation of the 2016 M 5.8 Gyeongju, South Korea, earthquake, using slip-weakening distance heterogeneity, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5500, https://doi.org/10.5194/egusphere-egu25-5500, 2025.
The Korean Peninsula, generally tectonically stable, has experienced occasional seismic activity, with 19 earthquakes of magnitude Mw ≥ 4.0 since 2013. The largest inland earthquake, a magnitude ML 5.8 event, struck Gyeongju in 2016, causing significant damage and casualties. It was preceded by a foreshock and followed by numerous aftershocks. In 2017, an ML 5.4 earthquake in Pohang, potentially related to enhanced geothermal system exploration, caused major damage. In 2024, a 4.8 ML earthquake occurred near Buan-gun, indicating continued seismic activity in the region. This study simulates the ground motions of the recent inland earthquakes, with a focus on the 2016 Gyeongju and 2017 Pohang earthquakes, along with their associated foreshocks and aftershocks, utilizing existing source and velocity model data and rise time scaling relationships. We investigated whether we can consistently simulate the recent Korean earthquakes with existing models and data, with an overarching goal of improving earthquake simulation accuracy for future applications in the Korean peninsula. The simulations were performed using the Spectral Element Method via SPECFEM3D, an open-source software for high-accuracy seismic modeling. We found that simulated ground motions were overall consistent with Gyeongju mainshock observations when an existing risetime scaling relationship was assumed. The results also showed some dependence on the assumed risetime scaling relationship for the Gyeongju and Pohang mainshocks, meaning that a region-specific scaling relationship might improve the overall accuracy of the simulation. We also found that the simulations were less dependent on the risetime scaling for earthquakes with magnitudes less than 5. Simulation of the 2017 Pohang mainshock was significantly underpredicting the recorded motions, when the simulation assumptions was consistent with the Gyeongju event. 2017 Pohang earthquake records were showing very pronounced surface waves that the simulation failed to reproduce using the current model. Simulations of smaller earthquakes showed varied levels of consistency. We are currently investigating the causes of the inconsistency in the simulation of recent earthquakes by comparing them with recorded motions, and we hope that we will eventually find a way to consistently reproduce earthquake ground motions for future applications.
How to cite: Layek, M. K. and Jeong, S.: Ground Motion Simulation of Recent Korean Earthquakes Using the Spectral Element Method, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2031, https://doi.org/10.5194/egusphere-egu25-2031, 2025.
We aim to simulate the wave propagation in the complex near-subsurface in urban environments. Here, we focus on the DESY and physics campus with its large underground accelerator tunnels in Hamburg, Germany. Since these particle accelerators, and other sensitive physics experiments on campus, are sensitive to seismic vibrations, it is important to understand how the seismic wavefield couples into the building structures.
To achieve this, there is a need to develop a high resolution subsurface model of Hamburg region. However, to model the whole seismic wave path in 3D for teleseismic events is computationally expensive. In order to circumvent this issue, the present work explores using RegHym package for earthquake simulation of teleseismic events. This package combines the efficiency of Axisem and flexibility provided by SPECFEM3D to embed the intricacies at regional scale in the model. This allows to simulate wave propagation for a teleseismic event on a regional scale in a computationally less-expensive way.
We are exploring the package to broaden its usability to model full waveforms of tele-seismic events for Hamburg area, incorporating the complex geological and urban environments. The subsurface model will be refined through consecutive comparisons of the synthetic data with data available from a DAS network implemented at the DESY campus in Hamburg. The real data from DAS will be enriched by incorporating recorded data from seismometers deployed in the vicinity of the DAS network.
The refined model will be a fundamental step for numerically investigating the coupling of incoming seismic waves into urban infrastructures as well as into gravitational wave observatories, which are sensitive to very small seismic disturbances.
How to cite: Hejazi Nooghabi, A., Dhabu, A., and Hadziioannou, C.: Developing a High-Resolution Subsurface Model through Teleseismic Wave Simulation in Hamburg, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18687, https://doi.org/10.5194/egusphere-egu25-18687, 2025.
The Campi Flegrei caldera, with its complex volcanic structure, represents an intriguing challenge for understanding seismic wave propagation. This study presents forward simulations of seismic wave propagation in the caldera area performed by using the spectral element method software SPECFEM3D (Peter et al., 2011). Moment tensor solutions for three seismic events that occurred between May and June 2024, including the Md 4.4 Solfatara earthquake, were considered. Simulations were performed using five different wavespeed models: (1) a 1D model without topography; (2) the same model incorporating the regional topography; (3) the local tomographic model from Giacomuzzi et al. (2024); (4) a 3D model including local attenuation from Calò & Tramelli (2018); and (5) the Italian 3D tomographic model Im25 by Magnoni et al. (2022).
Our approach aims to compare these models for the same seismic sources, in order to highlight the key factors influencing waveform fit between observed and synthetic data. Implementing high-resolution surface topography —characterized by volcanic structures, depressions, and abrupt variations—is crucial to improve waveform fit and reproduce seismogram behavior. Moreover, the results highlight the importance of adopting tomographic models with tailored attenuation and 3D velocity structures that effectively capture the lateral heterogeneities of such a complex area. This is especially crucial when modeling the Campi Flegrei caldera characterized by solidified intrusions and partially melted regions in order to achieve more accurate regional predictions.
Given the coastal setting of the considered area, we also investigate whether the presence of a water layer (i.e., acoustic elements), absent in current simulations, might influence the quality of the fit between observed and synthetic data. To this aim, we explore a simplified scenario that would be representative of the studied region.
How to cite: Fabrizi, F., Magnoni, F., Casarotti, E., and Tinti, E.: Investigating the role of topography and attenuation in volcanic areas by testing different structural models of the Campi Flegrei , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11229, https://doi.org/10.5194/egusphere-egu25-11229, 2025.
Simulating seismic wave propagation in 3D is a complex task, largely due to challenges in accurately representing the on-fault stress state prior to an earthquake. A common approach involves assigning initial fault stress by determining its normal and tangential components based on regional stress conditions. However, for faults with complex geometries (e.g., curved surfaces or overlapping sub-faults) and inhomogeneous material properties, this method often struggles to establish a stress state that aligns with fault geometry, residual stress concentrations, far-field loading, and material heterogeneity.
This study focuses on prescribing initial fault stress based on far-field deformation and the fault’s governing frictional behavior. This enables the assignment of a consistent stress state for faults with complex configurations and non-linear, heterogeneous material or frictional properties. Fault rupture is modeled as a dynamically propagating shear crack along a pre-existing fault plane according to rate-and-state friction. We use PDS-FEM due to its computational efficiency in modeling discontinuities.
To address the computational demands of large-scale numerical models, we propose an MPI+MPI hybrid approach, where MPI shared memory windows are efficiently managed using C11/C++11 atomic operations. Standard MPI RMA synchronization functions, such as MPI_Win_sync(), MPI_Win_fence(), etc., are designed conservatively, which can limit compiler optimizations and hinder out-of-order execution by hardware schedulers. By replacing these synchronization functions with C11/C++11 atomic operations and the associated multi-thread memory model, we achieve efficient management of MPI-3 shared memory windows. Performance tests demonstrate that this approach equals, and in some cases surpasses, more conventional methods, particularly for classical applications like ghost updates.
The fault rupture model was validated by reproducing supershear rupture in a 2D fault, illustrating the Burridge-Andrews mechanism. Furthermore, we analyzed the sensitivity of rupture behavior to initial stress conditions using the Palu-Koro fault as a case study, observing transitions between sub-Rayleigh and supershear regimes.
References
[1] Quaranta, L., Maddegedara, L., Kato, A., Hori, M., Ichimura, T., Fujita, K., & Nicolin, E. (2024). Large scale simulation of 3D fault rupture subjected to far‐field loading with PDS‐FEM: Application to the 2018 Palu Earthquake. Journal of Geophysical Research: Solid Earth, 129(9), e2024JB028783.
[2] Quaranta, L., & Maddegedara, L. (2021). A novel MPI+ MPI hybrid approach combining MPI-3 shared memory windows and C11/C++ 11 memory model. Journal of Parallel and Distributed Computing, 157, 125-144.
How to cite: Nicolin, E., Maddegedara, L., Quaranta, L., Fujita, K., Ichimura, T., and Hori, M.: Fault rupture simulation via physics-based prescription of consistent fault stress according to far-field loading conditions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7927, https://doi.org/10.5194/egusphere-egu25-7927, 2025.
Earthquakes are one of the most potent geological hazards. They may cause vital destruction, including casualties and property damage. Fluid plays an important role in the seismic cycle, along with tectonic deformations. Reservoir induced seismicity (RIS) linked to impoundment of artificial reservoirs and their water level changes, is usually characterized by higher magnitudes, compared to other types of natural and anthropogenic fluid-induced seismicity. However, there is still no comprehensive understanding of the RIS mechanisms despite previous high-resolution in-situ water level and seismic monitoring and their statistical analysis. This study suggests a fully coupled poroelastic model for fully dynamic RIS sequences simulations in a faulted reservoir. The model is thoroughly verified (e.g., on quasi-static Terzaghi and dynamic compressive poroelastic seismic wave propagation, and on other problems). Seismic sequence patterns simulated using a rate-dependent frictional contact under extension and with adaptive time stepping demonstrate proper characteristics applicable to tectonic earthquakes. These verifications and benchmarking demonstrate a convincing agreement with analytical predictions. The fluid flow within the rock and over the fault is modeled as well, being enhanced after the activation of a reservoir impoundment. The model allows further investigation of the RIS spatio-temporal characteristics and triggers. It also may allow for improving earthquake prediction and mitigation policy, especially in areas with substantial water level fluctuations.
How to cite: Zhou, X. and Katsman, R.: Fully Dynamic Model for Reservoir Induced Seismicity, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-287, https://doi.org/10.5194/egusphere-egu25-287, 2025.
Small earthquakes are frequently modeled as point sources or as ruptures with a simple circular geometry. While these representations are sufficiently accurate within a specific range of frequencies, the actual rupture processes of these earthquakes are inherently more complex.
Earthquake waveforms represent a convolution of source and propagation effects, requiring their separation to enable independent analysis of each component. To investigate the earthquake source, isolating the source time function is crucial. Kinematic rupture models are commonly constructed using Theoretical Green's Functions (TGFs), which rely on simplified one-dimensional (1-D) velocity models that incorporate anelastic attenuation and wave propagation. However, for small earthquakes, this method requires highly detailed structural models, which are often unavailable.
An alternative approach utilizes deconvolution with the Empirical Green’s Function (EGF), obtained from a smaller, co-located event recorded by the same instruments. In this study, we employed the EGF method to extract the source function for small earthquakes (Mw ~3.5) that occurred in the Alto Tiberina fault area. The Landweber deconvolution technique (Bertero et al., 1998) was applied, with a semi-automated selection of parameters, including the signal window and the maximum duration of the apparent source time function (ASTF), the latter based on the methodology proposed by Meng et al. (2020). When automated selection was not possible, we performed a parametric analysis to map the uncertainty on the final results corresponding to the different choice of possible parameters.
Additionally, we used the fault isochrone back-projection method outlined in Király-Proag et al. (2019) to investigate the kinematic source process of these events.
The findings show that this approach allows resolving finite fault properties and rupture directivity of small earthquakes, along with their related uncertainty.
How to cite: Cuius, A., Satriano, C., Supino, M., Tinti, E., and Chiaraluce, L.: Finite source analysis of small earthquakes using the fault isochrone back-projection method: examples from the Alto Tiberina fault., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13418, https://doi.org/10.5194/egusphere-egu25-13418, 2025.
During earthquakes, seismic ruptures propagate (Vr) along faults as mode II-III cracks, approaching the shear wave speed Vs (i.e., sub-Rayleigh or Vr ~ 0.9 Vs), or, in at least 15% cases, at Vr faster than Vs (i.e., supershear or Vr ~ √2Vs ) (Bao et al., 2022). Since ground shaking increases with rupture speed, the transition from sub-Rayleigh to supershear speeds is critical in seismic hazard studies. This transition may occur (1) directly, due to dynamic stress perturbations associated with stress and strength heterogeneities along the fault, presence of fault step-overs and damage zones, etc., or (2) in-directly, where the stress peak ahead of the main crack tip (mother crack) nucleates a secondary crack (daughter crack) once the local fault strength is exceeded (Burridge-Andrews model).
Here we employ a newly-conceived 2-dimensional hybrid Finite Element Method and Peridynamic (FEM/PD-2D) model to simulate crack propagation and investigate the transition from sub-Rayleigh to supershear in dry and fluid-saturated media, where the Finite Element Method is used to simulate fluid flow, while Peridynamics is used to describe solid deformation. The model also incorporates a novel bond failure criterion based on critical rotation deformation (i.e., deflection angle of the Peridynamic bonds before and after shear deformation) for mode II fracture propagation.
First, we validate the FEM/PD-2D model against previous results from (1) numerical simulations with ABAQUS by Yolum et al. (2021), and (2) physical experiments with PMMA by Svetlizky et al. (2015). In case (1), the FEM/PD-2D model accurately reproduces rupture propagation in a dry Homalite plate with a pre-notch subjected to impact shear loading. Supershear rupture is recognized by the emergence of shear Mach waves observed in the particle velocity magnitude contours. In agreement with Yolum et al. (2021), the stable supershear crack velocity lies between √2Vs and Vp (compressional wave speed). In case (2), the model reproduces the shear loading experiments of PMMA blocks with a frictional interface, and yields crack growth curves and supershear propagation consistent with the measurements of Svetlizky et al. (2015).
Subsequently, we apply the FEM/PD-2D model to explore rupture propagation along both dry and fully saturated media under shear loading. Supershear crack speeds and the emergence of shear Mach cones are observed in both the dry and fluid-saturated cases. Supershear rupture can be achieved through either the in-direct (Burridge-Andrews mechanism) or a direct transition. Notably, the presence of the fluid phase enhances the sub-Raileigh to supershear transition due to poroelastic effects at the rupture front. The findings from this model, beyond their implications for earthquake hazard assessment, may also explain the formation mechanisms of hundred-meter-thick rock damage zones adjacent to seismogenic faults.
How to cite: Shu, Y., Shen, Z., Ni, T., Faccenda, M., Galvanetto, U., Di Toro, G., and A. Schrefler, B.: Hybrid FEM-Peridynamic Modelling of Supershear Earthquake Ruptures, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2185, https://doi.org/10.5194/egusphere-egu25-2185, 2025.
Numerical simulations of Sequences of Earthquakes and Aseismic Slip (SEAS) have rapidly progressed to address fundamental problems in fault mechanics and provide self-consistent, physics-based frameworks to interpret and predict geophysical observations across spatial and temporal scales. Challenges in SEAS modeling include resolving the multiscale interactions between slow slip, earthquake nucleation, and dynamic rupture; and understanding the physical factors controlling observables such as seismicity and deformation. To advance SEAS simulations with rigor and reproducibility, we pursue community efforts to verify numerical codes in an expanding suite of benchmarks, including problems considering earthquake sequences on 2D and 3D fault models obeying rate-and-state friction with different treatments of inertial effects and fault dip under slow tectonic loading (Erickson et al., 2020; Jiang et al., 2022; Erickson et al., 2023).
Here we present code comparison results from a new set of benchmark problems that focus on aseismic processes and earthquake nucleation, including the influence of (1) changes in effective normal stress and pore fluid pressure due to fluid injection and diffusion and (2) different formulations of fault friction evolution. Benchmark problem BP6-QD-A/S/C is a 2D problem that considers a single aseismic slip transient induced by changes in pore fluid pressure consistent with fluid injection and diffusion in fault models with different treatments of fault friction, including rate-and-state fault models using the aging (-A) and slip (-S) law formulations for frictional state evolution, respectively, as well as a constant friction coefficient (-C). BP7-QD/FD-A/S is a 3D problem with a 2D rate-and-state fault considering a circular velocity-weakening asperity that can produce sequences of repeating earthquakes or alternating seismic and aseismic ruptures, under different considerations of fault friction evolution and inertial effects. Comparisons of problems using the aging versus slip law illustrate how models of seismic and aseismic slip can differ in the timing and amount of slip achieved with different treatments of fault friction, including for individual aseismic slip events induced by the same perturbations in pore fluid pressure for BP6.
We utilize simulations from different groups to explore how various numerical factors affect the simulated evolution of pore pressure and interaction between aseismic and seismic processes. We achieve excellent quantitative agreement across participating codes that utilize distinct numerical methods, by ensuring sufficiently fine time-stepping, large enough domain size for volumetric methods and consistent treatment of boundary conditions. Through these comparative studies, we seek to determine best practices for improving the accuracy and efficiency of SEAS simulations and develop quantitative metrics for benchmarking modeling results. These community-led exercises will foster the development of more realistic multi-physics SEAS models and their integration with geophysical observations, contributing to an improved understanding of fault dynamics.
How to cite: Lambert, V., Erickson, B., Jiang, J., Romanet, P., and Thakur, P. and the Sequences of Earthquakes and Aseismic Slip (SEAS) Community Code-Verification Initiative: Community Code Verification Exercises for Simulations of Earthquake Sequences and Aseismic Slip (SEAS): Effects from Fluids and Fault Friction Evolution, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14426, https://doi.org/10.5194/egusphere-egu25-14426, 2025.
The South Iceland Seismic Zone (SISZ) is characterized by a complex "bookshelf" fault system composed of multiple short, parallel, North-South oriented right-lateral and near-vertical strike-slip faults assisting crustal block rotation to accommodate the overall East-West sinistral transform motion. The tectonic strain release across the entire zone is known to occur with 130–140 years intervals, in sequences of moderate earthquakes, up to Mw7. The most recent earthquakes occurred in 2000 and 2008 and reached magnitudes Mw6.3-6.5. Despite its importance for mitigating regional seismic hazards, the seismic cycle in the SISZ remains poorly understood. Thus, we develop a rate-and-state friction-based sequences of earthquakes and aseismic slip (SEAS) model to investigate the long-term seismic behavior of the SISZ.
We utilize the open-source code TANDEM (https://github.com/TEAR-ERC/tandem), a discontinuous Galerkin volumetric solver, and perform 2D simulations on the supercomputer ELJA, operated by the Icelandic High-Performance Computing Centre. Quasi-dynamic simulations with rate-and-state friction are applied to single planar fault models with antiplane shear motion in a homogeneous, isotropic, linear elastic half-space. We model two separate faults within the “bookshelf fault system,” representing the east-western regions of the transform zone. The primary focus of our 2D models is to reproduce the recurrence pattern of the seismic cycle, including hypocentral depth, fault slip, and approximate magnitudes. To configure reliable simulation parameters, we explore diverse models with varying rate-and-state frictional properties, effective normal stresses, and critical slip distances as well as other crucial factors.
Preliminary results indicate recurrence intervals for SISZ earthquakes ranging from 104 to 130 years across the transform zone's western and eastern sections, which agrees well with the observational data. Incorporating varying seismogenic depths in separate models-12 km in the west and 15 km in the east-improves our hypocentral depth predictions. Our study demonstrates the effectiveness of using seismic cycle simulations empowered by high-performance computing with TANDEM, even with a simplified single fault model, to elucidate the seismic processes of the SISZ. The model adequately captures some key characteristics of the seismic cycle of the SISZ, highlighting its potential to inform future seismic hazard assessments in Iceland within the larger scope of the ChEESE-2P project (https://cheese2.eu/).
How to cite: Cubuk-Sabuncu, Y., Gabriel, A.-A., Halldórsson, B., Oryan, B., Yun, J., and May, D. A.: Towards seismic cycle modeling of the complex “bookshelf” South Iceland Seismic Zone, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17611, https://doi.org/10.5194/egusphere-egu25-17611, 2025.
Repeating earthquakes most often occur as frequent small magnitude events, with repeating time increasing with magnitude. The Bárðarbunga caldera however is a rare example where moderate magnitudes (Mw ≥ 5) repeat frequently. During the 6 months caldera collapse event (2014-2015), 77 Mw ≥ 5 earthquakes were recorded and, in the years following the collapse, observations show quasi-periodic Mw ≥ 5 events. Recent seismological field campaigns have provided further constraints on the caldera’s geometry, mapping out a ring fault structure and offering excellent depth constraints. The repetitive nature of the earthquake sequences and good structural controls, make this case especially suitable to investigate using Sequences of Earthquakes and Aseismic Slip (SEAS) models. Furthermore, the periodicity of the ring fault is well captured to the first order by adopting a Spectral Boundary Integral approach. To mimic the observed data, we project relatively relocated seismic events to a mesh representation of the ring fault; we then convert the projected point clusters into frictional parameter maps that define the distribution of the rate weakening and rate strengthening asperities in the simulation. Finally, we quantify the differences between the simulated results and the observed seismic data by comparing for example reoccurrence time, magnitudes and partial rupture characteristics. We use the JAX Python library to achieve well resolved simulations, realistic frictional parameters and domain size. This library provides tools such as Just-In-Time (JIT) and Ahead-Of-Time (AOT) compilation, automatic differentiation and vectorization, all of which significantly speed up runtime. Moreover, JAX provides a flexible framework for running code on different accelerators such as GPUs, drastically reducing code runtime for parallelizable operations such as FFT computations.
How to cite: Benedetti, G., Heimisson, E. R., Winder, T., and De Vries, Y. A.: Asperity cycle simulation using observed seismicity: Applications to the Bárðarbunga caldera, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13050, https://doi.org/10.5194/egusphere-egu25-13050, 2025.
The 2016 Mw 6.2 left-lateral strike-slip Tottori earthquake occurred in the central part of the Tottori Prefecture in the Chugoku region in western Japan. Published rupture models inferred either from geodetic or seismic data exhibit significant discrepancies. In this study, we perform a so-far missing dynamic rupture simulation to improve the understanding of the event. We utilize 3D finite-difference staggered grid code FD3D_TSN to simulate the dynamic rupture propagation assuming the classic linear slip-weakening friction law on a planar vertical fault. Synthetic seismograms are calculated using the representation theorem by convolving the obtained slip rates with Green's functions precalculated in 1D velocity models acquired for each station from a 3D model.
We utilize the fd3d_tsn_pt code to perform a dynamic source inversion with spatially variable prestress and friction parameters, formulated in a Bayesian framework, employing the Parallel Tempering MCMC approach to sample the posterior distribution of the model parameters. We use local low-frequency seismic waveforms (up to 0.6-1.2 Hz) and GNSS static coseismic displacements. We obtain posterior model samples with complex rupture propagation, discuss the inferred heterogeneous rupture parameters in a statistical sense, and compare them with previously published models. We evaluate correlations and trade-offs among kinematic and dynamic rupture parameters. We find that the slip-weakening distance increases in average linearly with distance from the hypocenter, which can be interpreted as an apparent feature substituting the effect of (umodeled) significant off-fault yielding. We also try to include the slip-strengthening (SS) area at shallow depths and find that it is an unnecessary feature for this event.
How to cite: Hronek, M. and Gallovič, F.: Inverse Physics-based Modeling of the 2016 Mw 6.2 Tottori Earthquake, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6559, https://doi.org/10.5194/egusphere-egu25-6559, 2025.
Moment magnitude (Mw) is widely accepted magnitude scale as a direct physical measure of the long-period seismic energy released at the foci and thus its reliable quantification is of great importance for accurate seismic hazard assessment studies (Onur et al., 2020). Yet, a robust estimation of Mw and radiated energy (e.g., apparent stress) over a wide range of magnitudes is difficult, mainly due to the existing strong lateral heterogeneous nature of the crust in various tectonic regimes. Additionally, the extrapolation or linking of short-period magnitudes like ML to Mw can often lead to significant bias (e.g., Shelly et al., 2022). To address this issue, we employ a coda envelope-based source spectral method, which uses a regional empirical calibration approach by lowering the threshold for reliable Mw and radiated energy estimation. In order to achieve this objective, in this study we analyzed three-component digital waveform recordings of 51 moderate local and regional earthquakes (ML ≥ 4.0) that occurred from 2013 to 2022 in and around the central North Anatolian Fault Zone (NAFZ), including the 18 April 2024 Mw 5.7 Sulusaray (Tokat) earthquake and the 23 November 2022 Mw 6.1 Gölyaka (Düzce) earthquake, both with two notable aftershocks. Data with 100 Hz sampling rate were collected from 51 broadband stations operated by the Kandilli Observatory and Earthquake Research Institute (KOERI) and the Disaster and Emergency Management Presidency (AFAD). Using the Java-based Coda Calibration Tool (CCT), which applies the empirical approach developed by Mayeda et al. (2003) and efficiently processes seismic coda envelopes (Barno, 2017) for further calibration, we successfully implemented the coda-derived source spectrum method to calculate apparent stress and moment magnitude (Mw) across different regions. Following the calibration with reference events (apparent stress and moment-tensor Mw’s), we plan to extend reliable magnitude estimation to smaller earthquakes (ML < 4.0), confirming robustness in these predictions. Our results provide a more thorough catalog of seismic events in the NAFZ, thereby contributing to improvement of regional seismic hazard assessments. This approach may also serve as a framework for reliable small-to-moderate earthquake analysis in other tectonically active regions, thus supporting broader seismic risk management efforts.
How to cite: Tekiroğlu, G., Kaya Eken, T., Mayeda, K., Roman-Nieves, J., and Eken, T.: Source scaling of earthquakes in and around the North Anatolian Fault Zone based on coda-derived source spectra: Toward a more accurate and unbiased Mw catalog, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-540, https://doi.org/10.5194/egusphere-egu25-540, 2025.
On February 6, 2023, two catastrophic earthquakes struck the Kahramanmaraş region, marking some of the most destructive seismic events in modern Turkish history. These earthquakes caused extensive loss of life and widespread destruction across southeastern Türkiye and northwestern Syria. The two earthquakes ruptured different fault segments with comparable magnitudes, generating exceptionally strong ground motions. Particularly, in the southern section of the fault rupture along the Amos fault segment, extreme ground motions were recorded. The earthquakes' complex rupture processes, characterized by sequential bilateral ruptures, varying rupture velocities and geometries, across branched fault segments, provide crucial insights into rupture dynamics and seismic hazard. Understanding the spatial variability of ground motions and the directivity effects associated with these complex rupture dynamics is essential.
This study focuses on analyzing the spatial variability of ground motions generated by the Mw 7.8 mainshock. By simulating ground motions on a regular grid across the affected region, we investigate the spatial distribution of ground motion intensity measurements and the rupture directivity effects. Using advanced kinematic rupture modeling techniques, simulations were performed with the Graves and Pitarka (2016) hybrid-source method, combined with Frequency-Wavenumber (FK) 1D Green’s functions computed for a regional velocity model. High-slip patches and stochastic small-scale slip variations were incorporated to create hybrid rupture models.
The simulations, validated against strong-motion data, effectively reproduced near-fault ground motions within the 0–3 Hz frequency range, allowing for near-fault ground variability analysis. This study provides valuable insights into the spatial variability of ground motion amplification patterns and their relationship with rupture directivity, enhancing our understanding of earthquake ground motion variability and seismic hazard.
How to cite: Artale Harris, P., Pitarka, A., Akinci, A., Tsuda, K., and Graves, R. W.: Ground Motion Variability During the February 6, 2023 M7.8 Kahramanmaraş Earthquake, Türkiye, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6323, https://doi.org/10.5194/egusphere-egu25-6323, 2025.
Large subduction earthquakes with magnitudes (Mw) greater than 8.0 are devastating events. Such large earthquakes remain poorly recorded due to their infrequent occurrence. This lack of observational data limits our ability to study rupture dynamics and accurately predict future broadband ground motion. To address these limitations, physics-based modeling has emerged as a powerful approach for understanding the rupture dynamics of large subduction earthquakes and associated ground motions. In this study, we analyze kinematic rupture processes and their influence on synthetic seismogram simulations. We revisit the rupture characteristics and ground motion variability for a large megathrust earthquake in Central Chile, the Illapel Mw 8.3 (2015). We use the data derived from the Bayesian inversion framework presented by Caballero et al. (2023) as input for the forward modeling of ground motion. To capture the finite source effects of a heterogeneous slip distribution, we discretize each sub-fault into point sources limited by a separation dependent on the maximum frequency resolution. With this in mind, we interpolate the seismic moment and define the rupture propagation across the rupture plane. We implement two different codes to compute the resulting ground motions: Axitra (Cotton & Coutant, 1997) and Pyrocko-GF (Heimann et al., 2019). Both codes employ distinct methods for Green’s functions computation and source representation, allowing a comparative analysis of their capabilities in reproducing strong motion. Pyrocko-GF efficiently handles low-frequency simulations with pre-computed Green’s functions, while Axitra provides broadband synthetic seismograms up to 20 Hz. However, with Pyrocko-GF it is also possible to reach high frequencies by adding Green´s functions to its FOMOSTO program. The synthetic seismograms were compared against strong-motion data, focusing on stations at a maximum of 5° of the hypocenter. Key parameters such as peak ground displacement, waveform similarity, and spectral content were analyzed. Additionally, we evaluated the impact of different source time functions on predictions. Our results provide insights into the importance of incorporating heterogeneous rupture scenarios for large earthquakes, as well as the challenges of modeling high-frequency ground motions using different numerical approaches. It is foreseen that our methodology and results will be used in a full physics-based seismic-tsunami hazard assessment for Central Chile.
How to cite: Buenrostro, A. M., Cotton, F., Jara, J., Crempien, J. G. F., and Jünemann, R.: Synthetic Seismograms from Physics-based Modeling of Heterogeneous Rupture for Large Subduction Earthquakes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6860, https://doi.org/10.5194/egusphere-egu25-6860, 2025.
Posters virtual: Mon, 28 Apr, 14:00–15:45 | vPoster spot 1
EGU25-8250 | ECS | Posters virtual | VPS21
Boundary integral spectral formulation for in-plane rupture propagation at non-planar bi-material interfacesMon, 28 Apr, 14:00–15:45 (CEST) | vP1.1
The effect of heterogeneity (dissimilar materials) and geometry constituting an interface is an important problem in earthquake source mechanics. These two parameters in the fault interface are responsible for complex rupture propagation and instabilities compared to the homogeneous planar interface. Here, a boundary integral spectral method (BISM) is proposed to capture the in-plane rupture propagation in the non-planar bi-material interface. The conventional traction BISM suffers from the disadvantages of hyper singularity and regularisation is needed (Sato et al., 2020; Romanet et al., 2020; Tada and Yamashita, 1997). So, we are utilising the representation equation arising from the displacement formulation devised by Kostrov (1966). It uses the elastodynamic space-time convolution of Green’s function and traction component at the interface. These displacement boundary integral equations (BIEs) are the inverse equivalent of traction BIEs. When applied to an interface between heterogeneous planar elastic half-spaces, these displacement BIEs have yielded simple and closed-form convolution kernels (Ranjith 2015; Ranjith 2022). Displacement BIEs of this kind have not been utilised to analyse fracture simulation for non-planar bi-material interfaces until now. We assume the small slope assumption (Romanet et al., 2024) in our formulation to get the required displacement BIEs. Also, we expand the displacement BIEs of a non-planar bi-material interface to the leading order to obtain the non-planarity effects. Finally, we present a general spectral boundary integral formulation for a non-planar bi-material interface independent of specific geometry and traction distribution in a small fault slope regime.
How to cite: Kumar, S. and Kunnath, R.: Boundary integral spectral formulation for in-plane rupture propagation at non-planar bi-material interfaces, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8250, https://doi.org/10.5194/egusphere-egu25-8250, 2025.
EGU25-14737 | ECS | Posters virtual | VPS21
Crack front waves under Mode II rupture dynamicsMon, 28 Apr, 14:00–15:45 (CEST) | vP1.2
Local heterogeneities on a steadily propagating crack front create persistent disturbance along the crack front. These propagating modes are termed as crack front waves. There have been numerous investigations in the literature of the crack front wave associated with a Mode I crack (for e.g., Ramanathan and Fisher, 1997, Morrissey and Rice, 1998, Norris and Abrahams, 2007, Kolvin and Adda-Bedia, 2024). It has been shown that the Mode I crack front wave travels with a speed slightly less than the Rayleigh wave. However, similar investigation of the Mode II rupture has got minimal attention. Although, Willis (2004) demonstrated that for a Poisson solid, Mode II crack front waves do not exist for crack speeds less than 0.715, explicit results on the speed of the crack front waves, when they exist, have not been reported in the literature. The focus of the present work is on a numerical investigation using a recently developed spectral boundary integral equation method (Gupta and Ranjith, 2024) to obtain the speed of the Mode II crack front waves. Further, the perturbation formulae for Mode II crack, developed by Movchan and Willis (1995) are exploited to validate the numerical results on the crack front wave speeds.
How to cite: Mouli, Y. S. C. and Kunnath, R.: Crack front waves under Mode II rupture dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14737, https://doi.org/10.5194/egusphere-egu25-14737, 2025.
