Seismica

CRESCENT Earthquake Dynamic Rupture, Earthquake Cycle, and Tsunami Code Verification Platform

Loïc Bachelot — 2026-08-12

Physics-based simulations are critical for understanding natural hazards. The increasing complexity of numerical codes requires benchmark exercises to verify that different computational methods yield consistent results when solving the same governing equations. Here, we present an open-access web platform designed for the verification of earthquake dynamic rupture, seismic cycle, and tsunami simulations. The platform architecture utilizes a modular, serverless backend on Amazon Web Services (AWS) to provide scalable file processing and visualization. A lightweight static web application provides a secure interface for uploading and managing results, while the browser-based data visualization enables interactive analysis of time series and surface grid data. By using structured JavaScript Object Notation (JSON) text files to define benchmark structures, the system remains fully extensible, allowing the addition of new scenarios without modifying the underlying software logic. The platform hosts the "The Tsunami Problem Versions" (TTPV) 1 & 2, two benchmarks for 3D fully coupled earthquake dynamic rupture and tsunami generation, and provides a framework for earthquake cycle models. This community resource aims to build trust in numerical simulations and facilitate long-term collaborative code verification as modeling software continues to evolve.

Performance of the 2021-2022 UPFLOW large ocean bottom seismometer array in the Azores-Madeira-Canary Islands region, Atlantic Ocean

Maria Tsekhmistrenko — 2026-08-05

The largest and longest ocean bottom seismometer (OBS) experiment so far in the Atlantic Ocean occurred as part of the UPFLOW project to better constrain upward mantle flow, which is crucial to understanding global mantle flow. UPFLOW deployed 50 and recovered 49 OBSs in a ∼ 1,000 × 2,000 km² area in the Azores-Madeira-Canary islands region with a station spacing of ∼110-160 km between June 2021 and August 2022. Most instruments had three-component broadband seismic sensors and hydrophones, and three different designs of OBS frames were used. Our analysis shows ∼91 % data completeness. Vertical-component long-period noise (T>∼30s) is reduced compared to previous experiments. The orientations of horizontal components were estimated from the polarisation of long-period body and surface waves from teleseismic events. Earth’s free oscillations with frequencies as low as ∼1.8 mHz are observed following two Mw > 8 earthquakes, and the signal-to-noise ratio of these observations is enhanced after applying tilt and compliance corrections. We show illustrative recordings and spectrograms of teleseismic and local events as well as non-seismic signals (whales, instrument resonances), demonstrating the wide variety and richness of UPFLOW data and their potential to address many outstanding questions in solid Earth sciences, oceanography, and marine biology.

Hydrophone deployment in underwater volcanic settings; new data for the community

Corentin Caudron — 2026-07-24

Hydroacoustics is an often overlooked tool for volcanic monitoring, capable of recording everything from the release of millimetre sized bubbles to small scale phreatic eruptions and gas blowouts. Over the last 4 years we have deployed hydrophones in a range of subaqueous volcanic environments, from oceans to crater lakes, at depths from 1 to 350 m. Here we report on these experiments, describe our observations and present the recordings for use by the wider scientific community.

The Impact of Mapper Experience and Data on the Quality of Geomorphic Fault Mapping

Malinda Zuckerman — 2026-07-14

Mapping of potentially active faults is critical to characterizing earthquake processes and surface rupture hazard. Geologists map tectonic faults from remote sensing datasets by interpreting tectonic landforms formed during past earthquakes. However, evidence for faulting is often ambiguous, incomplete, and challenging to interpret. Conventional wisdom suggests that mapping skill improves with experience. In contrast, prior work has shown that experienced geologists can still miss faults and disagree on fault location. To test whether, when, and to what extent mapping improves with experience, we designed a repeat mapping experiment involving 23 participants, ranging from undergraduate students to senior professionals. Each participant created regional-scale fault maps using pre-earthquake remote sensing data and a systematic, geomorphology-based approach. While professionals slightly outperformed students, some graduate students produced similar quality maps, and all participants missed identifying tectonic landforms indicative of future ruptures. Using participant mapped fault data, we quantify inter-mapper epistemic uncertainty in fault location to be between 55 and 117 m. Our work gives insight into approaches to improve fault mapping and suggests that experience beyond a graduate student level does not significantly improve mapping results.

Higher modes in the near surface: the influence of gradients

Brian L. N. Kennett — 2026-07-22

Higher modes of surface waves are more sensitive to the details of the wavespeed distribution with depth than the fundamental modes, and in particular to the wavespeed gradients within layers and the transition between layers. The character and dispersion of the various modal branches are readily envisaged with the aid of calculations of frequency-phase speed spectra for surface sources. Colour-coding of the three-component response is helpful in assessing the nature of the modes and the way that they interact with recording systems. The near-surface can have very variable wavespeed gradients, from slight in the presence of recent sediments to quite strong under compaction. In the presence of gradients the dispersion properties of higher modes are not well represented by models with just a few uniform layers even though this may be adequate for the fundamental mode. Where gradients are expected, direct parametrisation is beneficial, even if implemented with sequences of uniform layers.

SPDE-ETAS: Fast and accurate Bayesian inference for the spatio-temporal epidemic type aftershock sequence (ETAS) model

Sofiane Taki-Eddine Rahmani — 2026-08-07

The Epidemic-Type Aftershock Sequence model is a well-established point process framework for characterizing earthquake occurrences. Traditionally, ETAS parameters are estimated using maximum likelihood methods, where the background rate is smoothed by a Gaussian kernel density. More recently, a Bayesian formulation has been proposed, in which the background rate is modeled as a Gaussian Process prior, enabling a flexible semi-parametric estimation. However, this approach can become computationally demanding for large datasets due to the dense covariance structure of the Gaussian Process.
An alternative representation of the Gaussian Process is the Gaussian Markov Random Field, which offers a sparse precision matrix formulation that significantly reduces computational complexity. Building on this connection, we propose the Stochastic Partial Differential Equation ETAS model, where the Gaussian Process covariance matrix is replaced by a sparse precision matrix within a Log-Gaussian Cox Process framework. The precision matrix is constructed using the finite element method on a triangular mesh, and the log-prior of the Gaussian Markov Random Field is approximated via the Laplace approximation to accelerate computation.
The model is first validated on synthetic datasets to assess its accuracy and computational efficiency compared to the kernel-based and Gaussian Process epidemic-Type Aftershock Sequence approaches. It is then applied to the Italian earthquake catalog (1960–2025) to estimate the stationary background seismicity with its uncertainties, relevant for seismic hazard assessment.

Validation framework for semi-stochastic simulations in Cascadia earthquake early warning

Tara Nye — 2026-08-03

We generate a synthetic earthquake dataset for the Cascadia region and present a framework for validating simulations for use in testing earthquake early warning (EEW) performance. The Cascadia Subduction Zone (CSZ) offshore western North America has hosted ~M9 earthquakes (the most recent being in 1700 C.E.), but few moderate-to-large earthquakes have been recorded here on seismic instruments. Synthetic seismic and geodetic data provide a useful supplement to the paucity of recorded data necessary for testing EEW; however, no published study to date has validated simulations and their output for such applications. We use a set of 1D semi-stochastic forward modeling codes to generate 112 M6.6–9.4 CSZ rupture scenarios and waveforms for 191 sites between Oregon and British Columbia. We validate the waveforms based on features critical to EEW infrastructure, which include event detection success, magnitude estimation, and ground-motion intensities. We also present an example performance test of the ShakeAlert EPIC and Ocean Networks Canada early warning algorithms using six of the simulated events. Through the validation process, we find the simulated data represent real earthquakes scenarios well and to be a valuable component in the training of EEW algorithms for the Cascadia region.

Paleoseismic history of the causative faults of the 2019 Ridgecrest, California earthquake sequence

Ian K. D. Pierce — 2026-07-10

The July 2019 Ridgecrest sequence ruptured two nearly orthogonal faults, the left-lateral, NE-striking Salt Wells Valley fault (M_w6.4) and the right-lateral, NW-striking Paxton Ranch fault (M_w7.1), highlighting the hazard of multi-fault earthquakes in the Walker Lane. To test whether similar conjugate ruptures occurred previously, we excavated five paleoseismic trenches and constrained paleo-earthquake timing using luminescence ages. Salt Wells Valley exposures record the 2019 rupture and only one earlier surface-faulting earthquake (17-27 ka), indicating infrequent activity. In contrast, Paxton Ranch strata preserve two Holocene events (4.4-8.7 ka and 10.6-14.6 ka) and up to three late Pleistocene events (17 ka and older) in addition to 2019. These records indicate that rupture along the Paxton Ranch fault commonly occurs independently of the Salt Wells Valley fault. Slip rates based on 2019 displacements and these event intervals are 0.2-1.3 mm yr⁻¹ for Paxton Ranch and 0.01-0.09 mm yr⁻¹ for Salt Wells Valley. The 2019 sequence therefore represents an unusual pairing of an often-active dextral fault with a much less active sinistral fault. The contrasting recurrence and lack of overlap, together with regional paleoseismic patterns, indicate that synchronous rupture is not systematic but instead varies among faults within an evolving network. This suggests that seismic hazard reflects a fault system in which rupture is governed by time-dependent fault network interactions rather than independent, repeatable behavior of individual faults.

Improving seismicity monitoring to prepare for CO2 storage in the Horda platform, Norwegian North Sea

Hasbi Ash Shiddiqi — 2026-07-15

The Horda Platform in the Norwegian North Sea will host several awarded CO₂ storage licenses. This requires a robust understanding of background seismicity for site characterization and baseline monitoring. Offshore seismic monitoring is challenging when relying mainly on land stations, leading to poor azimuthal coverage and less precise locations. To improve monitoring in the Horda platform, we deployed three broadband ocean bottom seismometers (OBSs) during October 2021 to September 2022. We used ambient noise cross-correlations to validate OBS timing corrections, which also revealed Scholte waves consistent with the presence of soft sediments. We applied a deep learning-based detection algorithm to continuous OBSs and land data, followed by manual review. The resulting catalog, combined with the Norwegian National Seismic Network, reduced the magnitude of completeness to 0.8. Bayesian hierarchical relocation further refined event locations and increased confidence in detecting small earthquakes. The seismicity analysis revealed previously undetected offshore events, mainly north of the Horda Platform. These events are small and spatially scattered, but provide an improved baseline for seismicity characterization. Our work shows that long-term OBS deployment near the injection site enhances passive seismic monitoring plan for an offshore CO₂ storage site.

Fractal dimensions can lead to spurious interpretations of fault-rock character and slip physics

Randolph T. Williams — 2026-08-10

Cataclasis is defined by a combination of distributed microcracking and frictional sliding. These processes lead to mechanical wear and grain-size reduction along fault surfaces during both seismic and aseismic slip. A preponderance of research has utilized “fractal dimensions” extracted from fault-rock particle size distributions as a vehicle to infer the dynamics of strain accommodation and energy release during fault slip. Little work, however, has been done to quantitatively assess the validity of such metrics. Using a series of simple numerical experiments, we show that the fractal dimension provides an unreliable descriptor of fault-rock microstructures and the cataclastic processes that govern their evolution. Our results demonstrate that the most common approaches to estimating fractal dimensions during microstructural analysis are prone to previously unidentified measurement uncertainties. The magnitude of these uncertainties is large relative to what has been considered mechanically and seismologically meaningful by previous work. We conclude that errors inherent in the use of fractal dimensions have likely led to spurious interpretations of fault-rock character and slip physics over the last several decades.

Improving estimates of the b-value in regional catalogs by means of the the b-more-positive method

Eugenio Lippiello — 2026-07-25

The b-value, which controls the slope of the frequency-magnitude distribution of earthquakes, is a critical parameter in seismic forecasting. However, accurately measuring the true b-value is challenging due to the temporal and spatial variations in the completeness of instrumental seismic catalogs. In this study, we systematically compare traditional methods for estimating the b-value with newer approaches, specifically focusing on the b-more-positive estimator based on positive magnitude difference statistics. We conduct this comparison using both synthetic ETAS catalogs, with artificially introduced incompleteness, and instrumental catalogs from five regions: Japan, Italy, Southern California, Northern California, and New Zealand. Our analysis of synthetic ETAS catalogs demonstrates that traditional estimators systematically underestimate the b-value under incompleteness scenarios, whereas the b-more-positive estimator yields highly accurate results. Consistent patterns are found in instrumental catalogs, suggesting that conventional methods also underestimate the b-value in real datasets, with important implications for seismic forecasting. Moreover, the b-more-positive estimator provides robust evidence of significant differences in the b-value across the considered geographic regions.

Integrated seismic monitoring reveals subsurface evolution during volcanic inflation at Askja volcano, Iceland

Laure Brenot — 2026-07-13

Identifying volcanic transitions from quiescence to unrest and tracking subsurface evolution remains critically challenging. We analyzed continuous seismic records from Askja volcano (Iceland) from 2008-2024 using coda wave interferometry to track relative seismic velocity variations (dv/v) as a proxy for subsurface changes during renewed volcanic intrusion. This analysis is complemented with three additional methods: network covariance matrix analysis, Displacement Seismic Amplitude Ratio (DSAR) single-station analysis, and sensitivity kernel analysis, alongside GNSS, earthquake catalog, and meteorological datasets. Since August 2021, dv/v measurements revealed an abrupt transition from regular seasonal oscillations (±0.2%) to predominantly negative values reaching -0.7% near the inflation center, coinciding with 76 cm GNSS-detected ground uplift by August 2024. DSAR indicated higher seismic attenuation near the inflation source, suggesting volatile accumulation in the shallow subsurface through June 2022, followed by marked decreases associated with depressurization. Sensitivity kernel analysis demonstrated wave sensitivity reaches down to 3 km depth, encompassing the shallow reservoir levels. Integrated seismic observations revealed magma-induced seismic velocity drops, followed by system reorganization with frequency-dependent recovery, and finally establishment of a new state with hydrothermal circulation maintaining altered seismic properties. This approach demonstrates the effectiveness of continuous seismic monitoring for detecting volcanic unrest transitions and tracking evolving subsurface processes.

Seismo-Acoustic Meteoroid Observation Recording Database (SMORD): A Global Dataset and Deep-Learning Phase Picker for Meteoroid-Generated Air-to-Ground Coupled Seismic Waves

Dario Eickhoff — 2026-07-03

Meteoroids impacting Earth's atmosphere generate acoustic waves that can couple into the ground and can be recorded by dense, globally distributed seismic networks. Thus, these records complement optical and radar observations, especially since seismic stations also operate in cloudy weather conditions and during daytime. However, open datasets that link meteoroid events to labeled seismic waveforms are scarce, limiting the development of automated detectors for meteoroid-induced seismo-acoustic signals. We introduce the Seismo-acoustic Meteoroid Observation Recording Database (SMORD), compiled by cross-referencing public meteoroid catalogs (International Meteor Organization fireball reports; NASA CNEOS fireball catalog) with seismic archives. Continuous waveforms are manually labeled for the first clear meteoroid-related onset of air-to-ground coupled seismic waves using a three-level pick-quality scheme. SMORD v1.0 contains 310 meteoroid events and 3,295 labeled arrivals across a global station set. Using SMORD labels, we train a PhaseNet picker in SeisBench with station-level splits and augmentation. On test data, the model achieves 91% precision and 94% recall at a 0.5 decision threshold (area-under-curve value 0.89), with median absolute timing error of 0.02~s (90% within c. ±0.3 s). We demonstrate automated onset detection and trajectory reconstruction for an April 2025 Adriatic fireball, highlighting the values of SMORD for rapid post-event analysis.

Influence of Moho topography on seismic beamforming: implications for mantle scattering

Shubham Agrawal — 2026-07-19

Measurements of scattered seismic phases are used to infer the distribution of small-scale heterogeneities in the mantle, which in turn inform our understanding of mantle dynamics. Directionality of the wavefront can be measured at seismic arrays, and accuracy is essential, as even small deviations can significantly misplace the inferred location of these scatterers. However, near-surface structures under seismic stations may distort these directionality measurements. In this study, we assess how variations in crustal thickness affect array measurements across Alaska. We observe backazimuth offsets mostly within 5° of the great-circle path between source and array, with offsets varying systematically between sub-arrays for each event, indicating a receiver-side origin. We test the hypothesis that offsets are caused by P waves interacting with dipping Moho interfaces, and reproduce the observed offsets. We quantify how even modest tilts in the Moho (~6°) can deflect the wavefront and alter apparent arrival direction by observable amounts. These offsets can shift inferred scatterer locations by hundreds of kilometers, illustrating the need to correct for shallow structure in deep Earth imaging studies.

Paleoseismic evidence for surface rupturing earthquakes on the West Caspian Fault (Azerbaijan): an active right lateral strike slip fault zone in an over-pressured sedimentary basin

Neill Marshall — 2026-08-12

We provide the first geomorphic evidence for active right-lateral strike-slip faulting at the eastern margins of the Greater Caucasus and western margins of the South Caspian Basin. The West Caspian Fault comprises several parallel strands, exhibiting numerous right-lateral stream deflections, following mud volcano alignments. Mud volcanoes occur predominantly at bends and folds along the otherwise strike-slip trace, indicating a structural control on emplacement. Mud volcano distribution and alignments in seismicity allow us to infer a total fault length of ~150 km. We estimate a Holocene slip-rate of 3.9-4.8 mm/yr, based upon a displaced terrace riser of assumed age. Two paleoseismic trenches reveal between five and six surface rupture events over the last 3000 years, and an average recurrence interval of 500-600 years. The events are unevenly spaced in time, with a cluster of 3 events in the last 650 years, and longer intervals earlier. From earthquake scaling relationships we expect rupture of the entire fault length to produce Mw 7.5 events with average slip of 3 m, consistent with the smaller measured lateral offsets. However, a lack of historical earthquakes combined with inferences on fault behaviour within the fluid-rich over-pressured Kura basin sediments lead us to speculate that the ruptures may represent aseismic slip or low-magnitude surface-rupturing earthquakes.

Seismic Hazard on the Main Himalayan Thrust from Physics-Based Earthquake Simulations

Govinda Niroula — 2026-08-05

Seismic hazard assessment in the Himalayan region remains highly uncertain due to the limited historical record and complex fault behaviour. To help address this, we present a 10,000-year long catalogue of synthetic earthquake ruptures on the Main Himalayan Thrust (MHT), one of the most hazardous continental fault systems on Earth. Simulations were performed by implementing geodetic models of the MHT’s geometry and slip rate into the physics-based Rate-and-State Earthquake Simulator (RSQSim), which applies the concepts of rate and state-dependent friction to generate long-duration synthetic earthquake catalogues. The MHT catalogue we generated reproduces key characteristics of observed seismicity, including magnitude-frequency distributions, rupture extents, and spatial patterns along the MHT. A key result is that low-coupling zones, previously inferred from geodetic data, consistently act as rupture barriers in the simulations, effectively limiting the maximum magnitude to Mw 8.9. In addition, we implemented this MHT RSQSim catalog into a stochastic probabilistic seismic hazard assessment (PSHA) of Nepal and compared the hazard estimates to a conventional PSHA model. At 10% probability of exceedance (PoE) in 50 years, the maximum difference (RSQSim derived hazard - classical PSHA) in Peak Ground Acceleration (PGA) range from +0.1g (+20%) to -0.6g (-70%), while at 2% PoE in 50 years the differences are +0.3g (+30%) to -0.6g (-40%), and at 0.5% PoE in 50 years, it is +0.4g (+30%) to -0.7g (-40%). In relative terms, 84% of sites have an absolute hazard difference below 60% at 10% PoE in 50 years, while 84 % of sites have an absolute hazard difference below 30% for 2% and 0.5% PoE in 50 years. Our results suggest that physics-based simulations offer a valuable complement to conventional source models, particularly for faults with variable rheologies and limited earthquake records like the MHT.

Shallow subsurface imaging from footsteps recorded by DAS

Thomas Luckie — 2026-07-23

Characterizing the shallow subsurface seismic structure is essential for a broad spectrum of geophysical analyses, including seismic event detection, ground motion monitoring, and the assessment of anthropogenic activities. However, data collection in urban areas is often constrained by practical or logistical challenges associated with the deployment of sources and receivers, particularly in scenarios requiring dense seismic data acquisition. This study seeks to address the practical limitations of traditional seismic sources in urban areas by utilizing footsteps as a novel data source recorded by distributed acoustic sensing (DAS). We show that footstep-generated seismic waves can be effectively used to calculate shear wave velocities and perform reflection imaging of the shallow subsurface. By inverting dispersion curves from footstep data, we generated a 2-D shear wave velocity profile, which was compared to an existing 3-D model obtained from conventional active sources. Our results indicate that footstep sources can provide high-resolution subsurface imaging to depths of 25m, enhancing seismic models in urban environments where traditional methods may be less practical. This innovative approach offers a potential solution for improving our understanding of subsurface structures in earthquake-prone regions.

Crustal Thickness Variations Beneath the Western Indian Ocean Using Teleseismic P-Wave Coda Autocorrelations on Ocean-Bottom Seismic Data

Ali T S Saneesh — 2026-07-02

The western Indian Ocean is a key region for investigating lithospheric evolution, as it records a complex interplay of tectonic, magmatic, and mantle processes. Constraining crustal thickness across this area is therefore essential for understanding how these processes interact and shape the region's geodynamic development. In this study, we apply teleseismic P-wave coda autocorrelation to map crustal thickness across the western Indian Ocean using data from 54 ocean-bottom seismometers (OBSs) and 7 land-based seismic stations. Our results reveal pronounced lateral variations in crustal thickness, ranging from ~4.3 km beneath young oceanic crust near the Central Indian Ridge (CIR) to ~25.85 km along the eastern margin of Madagascar. The oceanic domain exhibits a mean crustal thickness of ~7.01 ± 0.27 km, consistent with global oceanic averages. Volcanic islands within the Mozambique Channel show crustal thicknesses between ~11.21 and 23.98 km, whereas those in the Mascarene Basin display values of ~10.73 km and ~14.63 km. These localized zones of crustal thickening beneath volcanic islands likely reflect long-lived magmatic underplating and hotspot-related intrusions. Collectively, these findings provide new quantitative constraints on the tectono-magmatic processes that govern crustal formation, modification, and isostatic compensation in this geodynamically complex region.

Fragility Modeling of Precariously Balanced Rocks: Calibration, Benchmarking, and Sensitivity

Zhiang Chen — 2026-07-15

Precariously balanced rocks (PBRs) provide natural geological indicators for constraining the upper bounds of earthquake ground motions over long timescales. However, translating these constraints into fragility models remains challenging because computationally expensive simulations limit inverse analysis and calibration of contact physics, reducing confidence in the fragility model predictions. To address the challenges, we present a simulated shake-table platform built on a physics engine. Using physical large-scale shake-table experiments on a natural PBR and 582 recorded earthquake displacement histories, we calibrate the contact parameters and benchmark overturning predictions against experimental results and a state-of-the-art discrete element method (DEM). The physics-engine approach reproduces overturning with predictive reliability comparable to DEM, while reducing wall-clock cost by approximately 10² to 10⁵ times. This efficiency enables large ensemble analyses and allows us to evaluate how uncertainty in contact parameters propagates into inferred fragility boundaries. Among the contact parameters, lateral friction exerted the strongest influence on PBR fragility, whereas restitution and spinning friction had comparatively minor effects, with contact damping and stiffness exhibiting more complex behavior. Our study establish a practical pathway for using PBRs as quantitative constraints in seismic hazard assessment.

Revisiting the causal factors of seismicity in the Dallas–Fort Worth area

Iason Grigoratos — 2026-07-23

The seismicity levels in the Fort Worth basin over the last 15 years have been elevated, with one earthquake above magnitude 4 occurring in 2015. Wastewater disposal (SWD) for oil and gas activities has been reported as the causal factor. We applied an established probabilistic framework to examine the extent to which either SWD or hydraulic fracturing (HF) are potential causal factors. Our framework employed new regional earthquake catalogs and established physics-based principles. We first hindcasted the seismicity rates after 2008 on a spatial grid using either HF or wastewater data as input, and then compared them against the null hypothesis of solely tectonic loading. We identified one unnamed sequence as induced by HF. A causal link between SWD and the Irving-Dallas and Lake Lewisville sequences is apparent for large diffusivity values. Curiously, our framework finds no significant link with SWD for the Venus, Azle or Cleburne earthquake clusters. That said, the method assumes a temporally consistent seismic response within each grid-cell, which does not appear to be the case in the basin. Rather, the basin is dominated by isolated sequences on a small percentage of faults. We conclude that the Fort Worth basin is not prone to widespread fault reactivation, allowing for effective mitigation measures.

Quantifying the erasure of earthquakes in desert landscapes

Malinda Zuckerman — 2026-07-14

Seismic hazard analysis depends in part on understanding fault segmentation and slip distribution, which are partially recorded in the landscape during surface-rupturing earthquakes. Over time, surface processes degrade these features, challenging fault mapping. We use landscape evolution models to quantify this information loss in desert environments. Using post-earthquake lidar from the 2019 Ridgecrest (California) and 2010 El Mayor-Cucapah (Baja California) ruptures, we simulate landscape degradation using 2D linear diffusion in Landlab over 100, 1k, 5k, and 10k years, with a transport rate of 1 m²/kyr. We assess change in mappable fault trace length, fault zone width, and a “degradation coefficient” based on topographic slope change. Field validation in 2024 (Ridgecrest) supports the modeled degradation. Results show that 20–80% of original fault trace length remains after 10k years and fault zone width decreases from a mean of 30 m to ~2 m, causing older rupture zones to appear narrower and less complex than initially. Degradation is fastest in the first 100 years, then slows. Fault zones with simple, single-strand morphology retain more mappable length and degrade more slowly. Fault zone structure primarily controls degradation rate and fault trace visibility. These findings provide quantitative constraints on landform degradation, informing probabilistic displacement hazard models and fault mapping in tectonically active regions.

Dense Seismic Array Monitoring of the Glacier Tongue of Isunnguata Sermia, West Greenland

Nicolas Paris — 2026-07-17

Accelerating mass loss from the Greenland Ice Sheet is affected by meltwater-driven changes in ice dynamics, which remain poorly understood due to limited observations. Here, we present a 2.5 km² wide dense passive seismic array experiment conducted in the ablation zone of Isunnguata Sermia, West Greenland. We target varying surface melt conditions through one-month long monitoring periods in spring, summer, and fall using 82-117 nodes deployed in 2023 and 2024 complemented by multi-week surface Distributed Acoustic Sensing acquisitions in 2024. We assess data quality using power spectral densities and noise correlation functions. We find that low-frequency seismic power is highly correlated to ice surface velocity, suggesting a strong control of subglacial hydrology on ice dynamics. We retrieve stable and high signal-to-noise ratio noise correlations containing Rayleigh, Love, and P wave arrivals, suggesting these may successfully be used for glacier structure imaging and monitoring. We finally demonstrate we can locate numerous seismic events with resolution down to a few meters using Matched Field Processing and which exhibit characteristic spatial patterns evolving across seasons. These findings establish the potential of such experiment to infer glacier hydrology, dynamics, and structure at high spatial and temporal resolution.