This study investigates an innovative approach to the earthquake location problem by simulating the use of Distributed Acoustic Sensing (DAS) technology deployed in a single vertical borehole. Traditional methods typically rely on extensive networks of seismometers distributed horizontally on the surface to accurately determine earthquake hypocenters. In contrast, this work examines the feasibility of deriving earthquake locations from DAS seismogram images recorded by 700 virtual receivers along a 3.5 km vertical cable in a well.
We evaluated multiple methodologies, including cross-correlation-based matching with a database of synthetic waveforms and advanced machine learning (ML) techniques such as convolutional neural networks (CNNs) and autoencoders. While the cross-correlation approach produced promising results for simple velocity models, it faced limitations when applied to more complex, realistic subsurface structures. To overcome these challenges, CNNs were employed to classify earthquake locations within a grid framework, and autoencoders were utilized to enhance the resolution of derived location images. The methodology was tested against two benchmark velocity models: the Marmousi model and a region-specific model derived from seismic exploration at a geothermal energy site.
Our findings highlight the potential of integrating DAS technology with ML for earthquake location imaging, particularly in environments with sparse seismic instrumentation. Our approach demonstrates promise in improving the efficiency and accuracy of seismic monitoring, especially in regions characterized by lateral velocity heterogeneities.
How to cite: Komeazi, A. and Rümpker, G.: Earthquake Location Imaging (ELI) for single-well Distributed Acoustic Sensing using Wavefield Classification, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18529, https://doi.org/10.5194/egusphere-egu25-18529, 2025.
Seismic tremor signals were recorded in 2021 by a temporary broadband seismic network deployed in the surroundings of the Domo de San Pedro geothermal field (DSPgf) in Mexico. A network-based covariance matrix approach was used to analyze those tremor-like signals, employing vertical-component data only. Seismic tremors were detected by identifying periods associated with low values of spectral width, defined as the width of the eigenvalue distribution of the network covariance matrix. These tremors occur in frequency bands ranging from 1 to more than 22 Hz, with durations varying from hours to months, and show higher amplitudes at closest stations to the active wells. The spectral characteristics of the DSPgf tremor-like signals reveal similarities to those found in volcanic and glacial environments, such as the presence of harmonic frequencies and spectral gliding. The sources of these tremor signals are located by back-projecting on a 3-D grid the dominant component of the wavefield obtained from the covariance matrix first eigenvector. Tremor locations indicate that the events originate within the zones of influence of the wells where geothermal operations occurred. We categorized four distinct tremor families based on spectral width signatures and compared them with detailed operational records. Our findings reveal that tremors at the DSPgf are associated with geothermal operations such as fluid extraction, wellbore maintenance, fluid re-injection, and changes in injection pressure. We propose a conceptual model of the first order tremor-generating mechanism for each tremor family.
How to cite: Muñoz-Burbano, F., Soubestre, J., Savard, G., Calò, M., Reyes-Orozco, V., and Ávalos, D.: Monitoring induced seismic tremor associated with fluid injection/extraction and mechanical operations at the Domo San Pedro geothermal field (Mexico), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19407, https://doi.org/10.5194/egusphere-egu25-19407, 2025.
Underground gas storage (UGS) systems are commonly used to balance seasonal fluctuations in demand and to secure strategic reserves by storing gas in geological trap formations. All underground industrial activities, including UGS, can affect the pore pressure and pre-existing stress state in seismogenic layers, potentially triggering earthquakes. Monitoring microseismicity in such a context is crucial, especially in urban areas. The study area of this work focuses on the Cornegliano Laudense UGS site, near Milan, one of 15 such sites in Italy, where the National Institute of Oceanography and Applied Geophysics (OGS) conducts seismic monitoring. In 2017, nine seismic stations were installed in accordance with national guidelines to establish a baseline of natural seismicity before the start of gas storage activities in December 2018.
Previous studies have shown that the central sector of the Po Plain has weak and deep seismicity due to crustal shortening between the Alpine and Apennine fronts. However, shallow seismicity has occasionally been recorded since monitoring began. Shallow seismicity was recorded both before and after the onset of storage activities, suggesting that it may be related to shallow tectonic structures. At the end of September 2024, the local seismic network detected its first seismic sequence, consisting of nine shallow microearthquakes with magnitudes between 0.9 and 1.3 ML and a depth of ~ 2.5 km. These seismic events occurred near a known thrust fault just outside the storage area.
We present preliminary results of a seismicity analysis performed to understand the origin of these shallow microearthquakes. Detection and location of such small earthquakes is challenging due to their low magnitude and low signal-to-noise ratio in this area. To improve detection, we applied a template matching technique based on the cross-correlation of continuous seismic data with well-located events, known as templates. This process revealed more than 150 seismic events throughout the entire monitoring period, with magnitudes ranging from -1 to 1.6 ML. Initially assigned to the locations of their templates, the hypocenter locations were refined by identifying P and S wave arrival times, where possible, applying both absolute (NonLinLoc) and relative (HypoDD) location methods. Our analysis also identified small clusters of past seismic events like those in the September 2024 sequence using a template matching method. For each sequence, we calculated composite focal mechanisms using the SKHASH code, combining polarities and S/P amplitude ratios for more reliable results. Finally, we examined seismicity diffusion patterns to assess potential fluid movement influences, as seismic events triggered by fluid intrusion often show characteristic spatial and temporal migration patterns.
How to cite: Fusco, M., Guidarelli, M., Romano, M. A., Sugan, M., Romanelli, M., Sandron, D., and Picozzi, M.: Application of methodologies for the analysis of microseismicity in industrial areas: a case study from underground gas storage in Cornegliano Laudense, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9387, https://doi.org/10.5194/egusphere-egu25-9387, 2025.
For the transition to a low-carbon future, carbon capture and storage (CCS) is a field of intense research worldwide. However, the process needs to be monitored closely for induced seismicity, and this in turn requires a clear picture of the background seismicity of the immediate area around the storage site. This study focuses on assessing the background seismicity of the Gulf of Kavala in Greece, where an offshore CCS pilot is deployed within EU project COREu. However, a major challenge associated with this area is the scarcity of catalogued events due to its low seismicity, as well as the sparse seismic station distribution, owing also to geography. To overcome this challenge, in this study, state-of-the-art AI-based seismic detectors (EQTransformer and PhaseNet) are used to re-evaluate existing recordings and enrich the area’s catalogue with low-magnitude events. A two-stage approach is considered to take into account and resolve the particularities of this involved task. In the first stage, we evaluate the baseline performance of the adopted pre-trained AI-based detectors, using data from the Corinth Gulf area, selected because the seismic network there is significantly denser and the seismicity higher. Specifically, for our purposes, we used data from a microseismic sequence of more than 400 events recorded in the first half of 2021, with magnitudes ranging from 0.1 to 1. In the experiment we utilize recordings of the selected events from a total of 50 stations located around the seismic sequence, with distances out to several tens of kilometers, to build a dataset with a wide and representative range of recording SNRs. To assess the detectability of the events, for each event/station pair, we measure the output of the detectors in a time-window of 5 seconds around the event arrival, forming a (detector) response magnitude vs SNR curve. This is used as a guideline for determining a detection threshold that strikes a good balance between true and false positives. Through this successful application of the method in the Corinth Gulf area, we gained significant knowledge about the limitations and the necessary configuration of the methods. In the second stage of the study, we conduct a preliminary detection experiment on continuous recordings from Prinos, utilizing data from stations surrounding the target area. The outcome of this experiment is evaluated by expert seismologists, using a specially created visualization tool for assisting the evaluation process. The adopted two-stage approach leads to the detection of a considerable number of low-magnitude, previously undetected events, constituting a significant first step towards assessing the implementation of CCS in the Prinos area.
How to cite: Pikoulis, E.-V., Mavrokefalidis, C., Ktenidou, O.-J., and Sokos, E.: AI-assisted assessment of low-magnitude seismicity in the area of Kavala-Prinos (Greece) , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20161, https://doi.org/10.5194/egusphere-egu25-20161, 2025.
Large fluid volume injections into the subsurface are increasingly common across a range of industrial and remediation activities. However, deep fluid injections are often associated with increased seismicity within a few hundred kilometers of the injection sites. The role of aseismic slip as an important precursory signal in induced-seismicity has gained importance in the community due to two reasons: (a) the time and length scales of injection-induced earthquakes are inconsistent with realistic diffusivities, and fluid-transport models do not match observations, and (b) modern theories of fault weakening suggest that at very high fluid pressures, faults can experience aseismic slip for prolonged periods before ultimately transitioning to unstable, seismic failure driven by static stress transfer.
Our work investigates far-field microseism triggering in NE Texas and NW Louisiana within the Haynesville shale-gas field that has developed since 2008. It includes the 2012 Mw 4.8 Timpson, TX earthquake, which has been attributed to wastewater injection. Seismicity from a temporary array and national monitoring show an increase in the number and magnitude of earthquakes in the area, with regular ML3 events near the Texas-Louisiana border. InSAR data indicate uplift around some injection wells. We consider multiple injection wells and compute the spatial distribution of geodetic strain rates derived from GNSS velocities and compare them with seismic strain rates from new earthquake data. In the decade following the 2012 event, several microseisms across the Texas-Louisiana border have been recorded, suggesting that critically stressed faults in the vicinity are being triggered in part by static stress transfer, as well as newer injection wells. We compare fault orientations to current stress, consider Coulomb stress change from the Timpson event, and use fluid transport models to explain the seismicity and vertical land motion observed in the Haynesville Shale play area.
How to cite: Arzabala, E., Sarma, P., Hurtado-Pullido, C., Musila, M., and Ebinger, C.: Fluid-Induced Aseismic Slip: Far-Field Triggering and Static Stress Transfer in the Haynesville Shale Gas Field, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3844, https://doi.org/10.5194/egusphere-egu25-3844, 2025.
The Western Canada Sedimentary Basin (WCSB) covers a vast area, extending from a zero edge along the Canadian Shield to the Canadian Cordillera in the west, where the basin is up to 7 km thick. Seismicity is largely concentrated within a ≈300km wide corridor, immediately east of the deformation front of the Canadian Cordillera. The northern half of the WCSB experiences natural earthquakes in the Mackenzie and Richardson Mountains, which are strongly influenced by plate-boundary interactions along the west coast of North America. To the south, seismicity in northeastern BC and western Alberta is characterized by localized induced (human-caused) seismic activity related to unconventional resource development during the last 15 years. This north-south partitioning of seismicity is reflected in Canada’s national seismic hazard maps, which consider only natural seismic hazards and highlight areas of relatively elevated seismic hazard in the Mackenzie and Richardson Mountains. However, since 2021 the seismic moment-release rates have become broadly similar in both southern and northern regions of the WCSB, despite relative seismic quiescence in the south from 2000 – 2014. Short-term seismic hazard maps for Alberta show localized areas of elevated seismic hazard that track temporarily and spatially varying levels of industry activity. The advent of large-scale carbon capture and storage (CCS) and geothermal projects could increase the potential for anthropogenic triggering of seismic activity.
How to cite: Eaton, D., Kao, H., Canales, M., and Shipman, T.: The big picture in western Canada: Induced seismicity from geo-energy applications is approaching the natural moment release rate of tectonically active northern regions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20644, https://doi.org/10.5194/egusphere-egu25-20644, 2025.
Monitoring induced seismic harzards during the fluid injections has been a significant challenge for geo-energy development. Conventional approaches, such as the (adaptive) traffic light protocol and prediction methods based on statistical and machine learning regressions, often yield limited accuracy due to diverse geological conditions across regions. A promising direction lies in developing precursors to monitor fault reactivation more effectively.
Recent seismological studies have shown that aseismic slip loading is more prevalent than previously thought during fault activation induced by fluid injections (Yu et al., 2021a, b; Eyre et al., 2019, 2022). Slow earthquake signals, like Earthquakes characterized by Hybrid-frequency Waveforms (EHW), occur during the transition from fault creep to brittle rupture induced by fluid injection (Guglielmi et al., 2015). These signals are potential indicators for aseismic slip loading and fault reactivation. However, their longer rupture durations distinguish them from typical induced earthquakes, rendering classic source analysis methods ineffective for real-time monitoring.
To address this limitation, we propose ASTF-Net, a machine learning (ML) model designed to predict Apperant Source Time Function (ASTF) by deconvoluting Empirical Green's Function (EGF) waveform from target waveform in time domain. This approach provides reliable real-time estimates of source durations, to identify slow earthquake signals, specifically EHW, and offers a valuable tool for fault activation monitoring. A robust and well-sampled dataset is therefore crucial for the model's performance.
In this study, we present a dataset designed for developing a single-channel version of ASTF-Net and evaluate its effectiveness using basic ML-models. The dataset consists of three parts: ASTFs, EGFs, and target seismic waveforms. Synthetic ASTFs are generated using kinematic forward modeling with an elliptical rupture model to simulate earthquake events with magnitudes ranging from Mw 3.0 to 4.5 and stress drops between 5 and 20 MPa. These random ASTFs are calculated under various ray paths. We collect EGFs from hydraulic fracturing-induced earthquakes (M1.5-2.5) in the Southern Montney Play, western Canada, recorded by a network of 40 nodal/broadband seismic stations between 2017 and 2020. Synthetic target waveforms are then created by convolving ASTFs with corresponding EGFs. The dataset’s inputs consist of single-channel synthetic seismic waveforms and their corresponding EGFs, with ASTFs as outputs. To assess the generalization and robustness of the model, records from different stations are divided into training, validation, and four test sets with varying difficulty levels based on geographical locations and event counts. Notably, Test level 4 is human analysis results reported by Roth et al. (2022).
We evaluate model performance using basic ML architectures, including MLP, CNN, VGG and U-Net. Performance metrics include the Correlation Coefficient (CC) between predictions and labeled ASTFs, and the relative error in apparent source duration. CNN emerges as the most promising candidate for the further optimization, achieving the following CC > 0.9 across test levels: 87.9% (Level 1), 85.9% (Level 2), and 80.3% (Level 3). The percentages of relative error below 10% are 59.3%, 59.3%, and 51.2%, respectively, for the three levels.
How to cite: Pang, R., Yu, H., Li, G., Meng, H., Liu, Z., Su, C., Zha, D., and Tian, W.: Dataset preparation for Resolving Apparent Source Time Functions (ASTF) and Evalutions Using Basic ML-models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7718, https://doi.org/10.5194/egusphere-egu25-7718, 2025.
The spatial distribution of hydraulic fracturing-induced seismicity is controlled by regional tectonics and local geological structures. In this study, we integrated a high-resolution shear velocity model from ambient noise imaging with 3D seismic reflection data to investigate structural influences on induced seismicity near an active hydraulic fracturing (HF) platform in the Sichuan Basin, China. We conducted continuous seismic monitoring throughout the fracturing period and located over 1,000 earthquakes within the 7 weeks of active stimulation. Tomographic model reveals a distinct first-order, EW-striking velocity boundary near the HF well. This lateral velocity discontinuity aligns closely with the 3D curvature attribute identified in seismic reflection data, with high-curvature areas corresponding to disrupted geological features like small-scale faults or stratigraphic discontinuities. Further quantitative analysis reveals that in addition to the spatial clustering near high-curvature areas, 70% of earthquakes are distributed on the high-velocity side and concentrated within a range of 500 meters from the HF well. Based on these observations, we infer that 1) the high-velocity anomalies are mechanically stronger and more susceptible to the release of cumulative elastic energy, and 2) pronounced attribute variations delineate the principal seismogenic structures responsible for hosting induced earthquakes. Consequently, regions with brittle rock properties and significant structural variations are more seismically sensitive under external fluid injection. Future work will involve applying the ETAS model to better understand the triggering mechanisms of induced seismicity, aiming to provide insights into the interaction between external fluid injection and localized stress perturbations.
These observations highlight the interplay between velocity heterogeneity, structural attributes, and localized stress perturbations in driving induced seismicity. Similar correlations between local velocity structure and earthquake nucleation are observed at a nearby platform, where the majority of over 6000 detected earthquakes are preferentially located near a NE-SW oriented high-velocity structure east of the injection well. Interestingly, both platforms are characterized by sharp topographic relief, with their maximum gradient well aligning with the velocity boundaries. These integrated structural features may prove crucial in identifying local geological structures that are prone to instability and assist strategy development toward risk mitigation of HF-induced seismicity.
How to cite: Zhang, F., Chen, Y., Wang, R., Yu, H., Rinaldi, A. P., and Ritz, V.: Structural Controls on Earthquake Clustering in Hydraulic Fracturing: Insights from Velocity Model and Seismic Reflection Data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7395, https://doi.org/10.5194/egusphere-egu25-7395, 2025.
Seismicity induced by water reservoir and fluid injection are widely known phenomena and have been studied for several decades. However, seismicity induced by crustal unloading in large open-pit mines are seldomly reported in the literature. Here we describe a case of seismicity associated with the large open-pit Cajati mine in SE Brazil, which has been operating for more than 40 years. The mine exploits carbonate rocks of a Mesozoic alkaline intrusion complex. The pit is 1.4 km long and 0.75 km wide reaching 300 m depth. The estimated amount of extracted rock is about 350 Mton. Nine earthquakes with magnitudes in the range 2.0-3.2 Mw have been recorded since 2009 by stations of the Brazilian Seismic Network (RSBR), some of them felt with intensities IV MM in nearby towns. The 2015 mainshock (3.2 Mw) caused expressive cracks in the mine benches, with up to 10 cm displacement. Epicenter relocation of the six largest events, using correlated P- and S-waves at regional distances, show that all events occurred in a single NNW-SSE oriented, 0.5 km long rupture aligned with the major axis of the pit, in agreement with the main trend of the micro-seismicity recorded by the local mine network. Focal mechanism was determined with two techniques: ISOLA envelope and FMNEAR using three stations at 100 to 160 km distance. Both methods show a reverse faulting mechanism with nodal planes oriented NW-SE to NNW-SSE. This is consistent with the expected mechanism for crustal unloading in open-pit mines. The Cajati mine is located in the Ponta Grossa Arch, in the coastal ranges of SE Brazil, a region with low-velocities at lithospheric depths. This suggests lithospheric thinning that concentrates stresses in the upper crust. In addition, the NE-SW P axis orientation is parallel to the coast line, a pattern that favors concentration of the regional stresses due to continental/oceanic structural transition. Aeromagnetic data shows a clear NNW-SSE regional fault crossing the mine area. The Cajati mine-induced seismicity is a classic case where several positive factors contribute to the inducing mechanism: a) high stresses in the upper crustal, b) favorable orientation of a previously existing weak zone (related to the NNW-SSE fault during emplacement of the alkaline body), and large Coulomb stress changes of about 4 MPa from unloading of the vertical stresses.
How to cite: Assumpcao, M., Schirbel, L., Nogueira, J. A., Carvalho, J., Dias, L., and Bianchi, M.: Seismicity Induced by a Large Open Pit Mine in SE Brazil: Combination of Stress Concentration and Crustal Weakness., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4842, https://doi.org/10.5194/egusphere-egu25-4842, 2025.
Risk modelling is a key tool for mitigating the seismic risk associated with geo-energy applications and CO2 storage. Prior estimation of potential damages and mapping of affected communities enable, among other things, the feasibility assessment of geothermal projects in their planning phase and the allocation of appropriate resources for damage compensation. This promotes societal preparedness and acceptance towards such applications.
With rising interest in geothermal energy in Switzerland, the Federal Office of Energy tasked the Swiss Seismological Service (SED) to extend the national Earthquake Risk Model ERM-CH23 (Papadopoulos et al., 2024) to include induced seismicity associated with geo-energy applications and CO2 injection projects. Since these activities typically trigger shallow earthquakes with low-to-moderate magnitudes, the need arose to extend the range of modelled intensity measures towards intermediate periods, which are more sensitive to potential damage from the expected scenario ruptures. As ERM-CH23 already covers PGV and PSA at 1, 0.6 and 0.3 s, it was decided to additionally integrate PSA(0.4s) and PSA(0.2s). From the perspective of soil amplification modelling, we first verified that the existing ERM-CH23 local response layers (Bergamo et al., 2023) are suitable for induced seismicity scenarios. We then applied the procedure of Bergamo et al. (2023), i.e., combining empirical amplification factors with site proxies via geostatistical interpolation, to generate the additional soil response layers for PSA(0.4, 0.2s). Leveraging an extended ground motion database and proven site condition indicators, the maps cover the whole of Switzerland while achieving a fine spatial resolution (250 m); the high quality of the input datasets contributes to keeping the associated (and mapped) epistemic uncertainty (ϕS2S) within reasonable limits.
In addition to seismic risk modelling, the complete set of national soil amplification maps for PSA(0.2 - 1.0s) has also been incorporated into the GRID approach of the current revision of SED's Good-Practice Guide for managing induced seismicity in deep geothermal projects (Kraft et al., 2025). GRID (Geothermal Risk of Induced seismicity Diagnosis, Trutnevyte & Wiemer 2017) is a diagnostic tool developed to classify a project's induced seismicity risk. The PSA(0.2 - 1.0s) amplification maps have been collated to consistently chart soft soil areas (soil types D, E and F of the Swiss building code SIA 261) at the national scale, contributing to GRID’s “local amplification” indicator.
References
Bergamo, P., et al. (2023). A site amplification model for Switzerland based on site-condition indicators and incorporating local response as measured at seismic stations. Bull Earthquake Eng 21, 5831–5865. https://doi.org/10.1007/s10518-023-01766-z
Papadopoulos, A. N., et al. (2024). The Earthquake Risk Model of Switzerland, ERM-CH23, Nat. Hazards Earth Syst. Sci., 24, 3561–3578, https://doi.org/10.5194/nhess-24-3561-2024
Kraft, T., et al. (2025). Good-Practice Guide for Managing Induced Seismicity in Deep Geothermal Energy Projects in Switzerland, Version 3, Report of the Swiss Seismological Service (SED) at ETH Zurich, pp. 80, https://10.3929/ethz-b-000714220
Trutnevyte, E., & S. Wiemer (2017). Tailor-made risk governance for induced seismicity of geothermal energy projects: An application to Switzerland, Geothermics, 65, 295-312, https://doi.org/10.1016/j.geothermics.2016.10.006.
How to cite: Bergamo, P., Sunny, J., Grigoratos, I., Roth, P., Kraft, T., Panzera, F., and Wiemer, S.: Modelling soil response at the national scale for Switzerland in the framework of risk assessment of induced seismicity, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8121, https://doi.org/10.5194/egusphere-egu25-8121, 2025.
Triggering of earthquakes due to the filling of dam reservoir is attributed to mechanical disequilibria, build-up by pore pressure diffusion driven differences in deformation and stresses in the subsurface rocks, ultimately compensated by the reactivation of faults. This kind of earthquake, also known as Reservoir induced seismicity (RIS) has the characteristics of small magnitude, high intensity, shallow source and long period. In some cases, seismic activities have lasted for several decades after the initial impoundment (e.g. in Koyna-Warna, India). Various approaches have been made by researchers to comprehend the role of water reservoirs in triggering such unique events. Modeling fluid-induced earthquakes requires coupling geomechanics, flow through porous media, and fault friction. A 2D poroelastic finite element model has been employed, incorporating coupled pore fluid diffusion and stress analysis along with contact interaction coupled to rate-and-state friction law, to simulate the stress change, deformation in rocks and fault slip due to reservoir impounding. Rate-and-state friction has been used with an aim to develop a modelling framework that can capture multiple earthquake sequences in order to understand the protracted RIS phenomenon. A fault is embedded in a 2D subsurface domain as contacting surfaces, the frictional behaviour along the fault surfaces is prescribed using a user subroutine FRIC in ABAQUS/Standard. The rate-and-state law has been defined in the subroutine. The ability of the subroutine to simulate multiple events of stick-slip motion has been checked using a simple spring-block slider analogy. The fault model is first initialised by simulating the in-situ field conditions, geostatic stresses are defined in the domain, frictional contact at the fault is established and zero pore pressure conditions are defined. After which, reservoir loading is applied on the top surface of the domain over a transient consolidation step and the pore pressure evolution down at the fault is studied. The decrease in fault strength is a result of increase in pore pressure that reduces the effective normal compressive stresses. The stress path, accumulated slip and friction coefficient at the midpoint of the fault is observed. The fault remains locked at the beginning, while the effective normal stress continues to decrease, at a point the fault strength drops and it starts to slip. Friction coefficient increases at the onset of slip, which is known as the direct effect, then decreases as the slip accelerates. Later, the fault rupture is arrested and the friction coefficient goes back to a higher value gradually. While simulating rupture in the fault, the contact interaction undergoes chattering when the fault slips abruptly, causing simulation to fail. In a non-dynamic analysis, instabilities will occur as the strain energy released due to fault slip cannot be dissipated. Contact damping has to be specified to dissipate the released energy. In the present study, only one event of fault slip has occurred. Increase in the pore pressure near the fault due to reservoir loading is not high enough for a second slip event.
Keywords: Reservoir Induced Seismicity, Poroelasticity, Rate and State Friction, Fault Slip
How to cite: Chakraborty, A., Gautam, S. S., and Dey, A.: Modeling Reservoir-Induced Seismicity using Rate-and-State Friction law , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19220, https://doi.org/10.5194/egusphere-egu25-19220, 2025.
A three-dimensional quasi-dynamic finite element method is developed to simulate fluid-induced seismicity on faults governed by rate-and-state friction. The coupled nonlinear hydro-mechanical equations governing both the fault and the surrounding rock matrix are solved simultaneously using the Imperial College Geo-mechanics Tool (ICGT), providing fluid pressure and displacement fields. This work highlights enhancements made to the friction module of ICGT, specifically the implementation of the augmented Lagrangian method to enforce fault surface contact constraints. This approach leverages the strengths of both the penalty method and Lagrange multipliers within the finite element framework. A stick-predictor slip-corrector algorithm is developed for the rate-and-state friction law to improve the convergence of the solution. The proposed numerical model captures the dynamic response of a fault to fluid injection, with the fault represented explicitly as a zero-thickness interface element in the mesh. To account for radiation damping effects and prevent unbounded slip rates within the quasi-dynamic framework, a velocity-dependent cohesion term is introduced into the shear stress formulation. The results emphasize the importance of selecting appropriate spatial mesh sizes and temporal time steps to ensure the convergence of the iterative Newton-Raphson solver. The simulation results show that pore pressure changes initiate an aseismic slip front that propagates along the fault, leading to failure in seismogenic zones. This method successfully captures all stages of the seismic cycle, including the transition from stick to slip behavior.
How to cite: Hosseini, N., Paluszny, A., and Zimmerman, R. W.: Fluid-Driven Slip on a Three-Dimensional Fault with Rate-and-State Friction: A Finite Element Analysis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6205, https://doi.org/10.5194/egusphere-egu25-6205, 2025.
The connection between fluid pressure, reservoir permeability evolution, slow-slip events, and the triggering of larger earthquakes remains a crucial but unresolved issue in the study of fluid-induced seismicity. Understanding these interactions is essential for seismic hazard mitigation and optimizing subsurface fluid injection productivity.
Discrete Fracture Networks (DFNs) are commonly used to study hydraulic diffusion and seismic activity within fault systems. However, traditional DFN models often rely on quasi-static assumptions and a simple Mohr-Coulomb criteria for earthquake triggering. These limitations hinder their ability to capture dynamic phenomena, such as self-propagating slow-slip events, and they provide little insights into the earthquake dynamics.
This study addresses these gaps by developing a 2D DFN model capable of simulating both fluid-induced slow-slip events and the potential for earthquake triggering. The model integrates hydraulic diffusion and slip processes governed by rate-and-state friction across several interacting faults within an impermeable, elastic rock matrix. A key innovation of this model is the dynamic evolution of fault permeability, which depends on normal traction changes and accumulated slip, consistent with laboratory and in-situ experiments.
The model was applied to two scenarios, both with and without permeability evolution: (1) fluid injection along a primary rough, rate-strengthening fault, where slow slip events occur and subsequently triggers microseismicity on secondary, smaller faults; and (2) fluid injection within a network of rate strengthening intersecting faults, where fluid diffusion reactivates slip throughout the network. In both cases, the simulated slow-slip events propagate faster than the fluid pressure diffusion front.
Interestingly, the migration patterns of microseismicity in the first case and slow slip in the second resemble diffusion processes, yet exhibit diffusivity values distinct from the imposed fault’s hydraulic diffusivity. This finding suggests that estimates of hydraulic diffusivity based solely on microseismicity front migration may not be accurate, in line with previous experimental and modeling studies.
These results highlight the influence of variable permeability and stress transfer caused by slow slip transients, offering valuable insights into induced seismicity within crustal reservoirs.
How to cite: Romanet, P., Scuderi, M. S., Ampuero, J.-P., and Cappa, F.: Impact of variable permeability in fault networks on fluid-induced seismicity dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5744, https://doi.org/10.5194/egusphere-egu25-5744, 2025.
Earthquakes that occur during geothermal exploitation or any other fluid-injection activity (hydraulic fracturing, CO2 waste disposals…) are attributed to the reactivation of rapid slip along critical faults. This highlights the urgent need of comprehensive monitoring and mitigation strategies to ensure both energy production and environmental safety.
Our main objective is to develop numerical methods to infer the permeability enhancement during fault reactivation induced by fluid injection in the laboratory. To this end, we model an experimental protocol conducted on a rock sample with a saw-cut fault, led by F.X. Passelègue and collaborators from the EPFL and GéoAzur rock mechanics laboratories. At the beginning of the injection experiments, pore pressure was uniformly set to 10 MPa along the fault plane. The injection experiment was preceded by a loading phase, during which shear stress was increased to approximately 90% of the peak shear stress to bring the fault to a critically pre-slip state. Fluid was then injected along the fault at a constant rate of 1 Mpa/minute, with simultaneous measurements of pore pressure, slip, and shear stress recorded continuously.
To simulate the experimental process, we established a system of coupled partial and ordinary differential equations that describe the evolution of key variables, including permeability, porosity, fault slip, and pore pressure. These equations are solved numerically. The general behavior of our key variables generated by the model reproduces the trend observed in the data recorded in the laboratory. For an advanced data match we develop a deterministic inversion approach, specifically the adjoint state method, to infer the permeability model. We are currently focused on enhancing this inverse model.
How to cite: Ben Khaled, I., Dublanchet, P., Chauris, H., Passelegue, F., and Blanco Martin, L.: Inferring Permeability Enhancement During Fluid-Induced Fault Slip Reactivation In The Laboratory, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16675, https://doi.org/10.5194/egusphere-egu25-16675, 2025.
Fluid injection-induced earthquakes present a significant challenge for geo-energy applications, such as geothermal systems and CO2 storage. Understanding the earthquake magnitude and frequency in response to fluid injection is of vital importance. Both the pressure and pressure rate are considered dominant parameters for the occurrence of induced earthquakes. Theoretical analyses of a spring-block model [1] have demonstrated that the reservoir response depends on the nondimensional pressure rate, defined as the ratio of the characteristic time of frictional slip to that of pressurisation. The pressure rate effect is most pronounced when this ratio falls within a narrow range of 10-4 to 10-3. These results have contributed to the interpreting laboratory experimental observations, however, the correlation between the injection rate and induced earthquakes at the field scale remains poorly understood.
This work develops a coupled hydro-mechanical model to simulate constant-rate fluid injection into a reservoir adjacent to a sealing, steeply-dipping, rate-and-state frictional fault, aiming to evaluate fault activation behaviour and the associated induced earthquake magnitude and frequency. The fault is modelled as a rate-and-state frictional contact with Mohr-Coulomb fault strength, and deemed to be reactivated when the shear traction on the fault exceeds the fault strength (frictional resistance), which depends on the fault sliding velocity. Rate-and-state fault slip dynamics are resolved using frictional contact modelling through a fully implicit, monolithically coupled finite element formulation. The fault is characterised by velocity-weakening frictional properties, allowing it to slip multiple times during fluid injection. A seismicity rate model is used to simulate the induced seismicity rate along the fault during fluid injection. Given that the nondimensional pressure rate depends on both the critical slip distance (related to the characteristic time of frictional slip) and the injection rate (related to the characteristic time of pressurisation), different combinations of the two parameters within the typical range of field values are examined to investigate the pressure rate effect on induced earthquake magnitude and frequency and seismicity rate.
Results have shown that the critical slip distance affects both the magnitude and frequency of induced earthquakes, whilst the injection rate primarily controls the frequency of induced earthquakes in typical field conditions. Notably, the induced earthquake frequency, along with the induced seismicity rate, shows a positive correlation with the pressure rate. However, the maximum induced earthquake magnitude does not appear to be significantly affected by the pressure rate within the typical range of field conditions. Based on the model results, the range of nondimensional pressure rate, within which the pressure rate effect is significant in field reservoir conditions, is identified. Outcomes of this work may provide valuable guidance for regulating injection rates to mitigate fluid injection-induced earthquakes in geo-energy applications.
Reference
[1] Rudnicki, J.W. and Zhan, Y., 2020. Effect of pressure rate on rate and state frictional slip. Geophysical Research Letters, 47(21), p.e2020GL089426.
How to cite: Cao, W. and Ma, T.: Pressure rate effect on the fluid injection-induced earthquake magnitude and frequency, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5080, https://doi.org/10.5194/egusphere-egu25-5080, 2025.
Injection-induced earthquakes (IIEs) are commonly attributed to pore-pressure elevation and associated Coulomb stress changes, leading to widespread adoption of Traffic Light Systems (TLS) that primarily focus on injection rate modulation for hazard mitigation. However, recent field observations have identified aseismic slip as an alternative mechanism for fault reactivation during direct fault-zone fluid injection, with evidence showing that slip propagation can outpace fluid migration fronts. Despite these insights, the critical conditions that determine when aseismic slip becomes the dominant mechanism—particularly the role of injection parameters—remain poorly understood. Here, we present direct fault-injection experiments equipped with high-resolution monitoring of fault slips and fluid difussions. Our findings reveal two fundamental insights into IIE mechanisms: (1) When faults are subjected to specific combinations of injection rates and pre-stress conditions, aseismic slip can initiate and propagate beyond the fluid-pressurized zone, becoming the primary mechanism for IIEs. (2) In near-critically stressed faults, the maximum seismic moment release may remain elevated even after injection rate reduction, undermining a core assumption of TLS protocols. Overall, these observations highlight that fault stress conditions, rather than injection parameters alone, dictate the upper bound of seismic hazard.
How to cite: Wang, C., Wang, P., and Xia, K.: How Does Injection Rate Control Injection-Induced Earthquakes?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19763, https://doi.org/10.5194/egusphere-egu25-19763, 2025.
There is still uncertainty in the mechanisms controlling the increase in earthquake productivity and shale gas development in the southern Sichuan basin of China. In this study we take advantage of a more complete seismic catalog from local seismic stations, as well as injection data for two adjacent hydraulic fracturing wells, during March 2017 to January 2018, to investigate these mechanisms. To ensure the completeness and reliability, two seismic catalogs were effectively merged and uniformly scaled using the moment magnitude Mw scale. A spatiotemporal constraint framework was designed to extract induced earthquakes during the injection stages, and a series of seismic statistical methods were used to study the correlation between 885 earthquakes (Mw 0 to 4.6) and fluid injection. These include the ETAS model, and the nearest-neighbor-distance method. The results suggest most seismicity close to the wells are likely linked to the hydraulic fracturing process. For events associated with the N5 well pad, the cumulative number of earthquakes has a positive correlation with the cumulative injection volume. Through the use of the Seismogenic-Index, the difference of seismogenicity of different wells is obtained. We show that injected volume not only correlates with the number of induced earthquakes, but also correlate with the maximum seismic magnitude in the region. We demonstrate that this can then be used to retroactively forecast the induced seismicity. Although the injection at the two well pads is similar, the N5 pad is associated with many more indued events compared to the N7 pad. Reflection seismic imaging indicates that faults and fractures are well developed beneath the target reservoir of N5, but not for N7. This indicates proximity to preexisting faults/fractures control the occurrence of inducing seismicity in the region. The possible cause of the Mw 4.6 earthquake is briefly analyzed by calculating the range of pore pressure diffusion, and the Coulomb stress change from poroelastic effects. This shows that induced seismicity in the southern Sichuan basin is controlled by both preexisting faults/fractures and injection fluid volume.
How to cite: Hu, J.: The productivity of induced seismicity in the southern Sichuan basin, China is controlled by injected volume and preexisting faults , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13985, https://doi.org/10.5194/egusphere-egu25-13985, 2025.
The world's energy supply depends critically on hydraulic fracturing (HF): HF operations utilize microseismicity to enhance subsurface permeability, so that hydrocarbons or geothermal heat can be extracted economically. Unfortunately, HF also has the potential to induce larger earthquakes – with some projects being prematurely terminated because of perceived earthquake risks. To de-risk HF, we use a suite of novel statistical tests called CAP-tests to discern if some physical process has restricted the growth of earthquake magnitudes. We show that all stage stimulations at UK PNR-1z indicate bound fracture growth, implying a more controllable operation. Contrastingly, stimulations at Utah FORGE and UK PNR-2 sequentially transitioned into unbound fault reactivation. The problematic stages (that ultimately led to the termination of PNR-2) are clearly distinguishable using CAP-tests. We postulate that our research can discriminate fracture stimulation from fault reactivation, contributing to the de-risking of HF operations worldwide.
How to cite: Schultz, R., Lanza, F., Dyer, B., Karvounis, D., Fiori, R., Shi, P., Ritz, V., Villiger, L., Meier, P., and Wiemer, S.: The bound growth of induced earthquakes could de-risk hydraulic fracturing, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-110, https://doi.org/10.5194/egusphere-egu25-110, 2025.
Induced seismicity related to industrial operations including carbon storage, geothermal energy, hydraulic fracturing or wastewater disposal has become increasingly common over the last 15 years. To continue these operations with minimal impact on sites, populations and economic conditions of the operation, it is crucial to better understand the mechanisms that control induced earthquakes and the occurrence of these in both space and time.
This research focuses on enhancing statistical forecasts (using the seismogenic index model and ETAS), specifically for CO2 storage applications. This forecasting is essential for estimating the hazards associated with the operational life cycle of these sites. Additionally, based on these forecasts, we explore operational management strategies, aimed at providing real-time feedback and suggestions to operators. All model calibrations were performed using data from the Illinois Basin Decatur Project – a pilot CO2 storage initiative with injection performed from 2011 to 2014. The resulting forecasts are included within an ensemble forecast within the open-source Operational Forecasting of Induced Seismicity (ORION) toolkit.
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
How to cite: Geffers, G.-M., Wang, C., Sherman, C. S., and Kroll, K. A.: Statistical Models to Forecast Induced Seismicity in CO2 Storage , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11791, https://doi.org/10.5194/egusphere-egu25-11791, 2025.
The injection of water during hydraulic fracturing leads to effective normal stress reduction on faults and may trigger earthquakes. Different injection loading schemes may lead to various slip behaviors in fault zones. In addition to direct pressurization (i.e., direct reduction of effective normal stress), cyclic pressurization has also been introduced. In this study, to reveal the underlying seismic triggering mechanisms during hydraulic fracturing, we employ double direct-shear tests to investigate the frictional behaviors of fault gouges under sine-shaped normal stress oscillation (NSO) and direct reduction of normal stress, conducted at a reference background normal stress of 40 MPa and constant shear stress (CSS) conditions. In all experiments, during the slip process, the fault slip velocity initially increases (slip-acceleration stage) and then decreases (slip-deceleration stage). NSO can significantly reduce the peak slip velocity of a fault compared to the direct reduction of normal stress. Faults sliding at a higher acceleration rate during the slip-acceleration stage also show a higher deceleration rate during the slip-deceleration stage. Repeating the NSO on the same fault under identical conditions causes a gradual decrease in its peak slip velocity, indicating permanent changes in the fault during slips. Various factors, including the compaction effect on healing and the rate of normal stress reduction, control the different slip behaviors triggered by NSO. Quantifying controlling factors in the field and optimizing NSO parameters can effectively reduce the potential of seismic activity, which is critical for safe hydraulic fracturing operations.
How to cite: Gao, K. and Zhang, L.: Effects of Normal Stress Reduction on Seismic Triggering, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20902, https://doi.org/10.5194/egusphere-egu25-20902, 2025.
Developing geothermal energy projects require a clear understanding of seismic hazard potential in the subsurface, specifically, fault reactivation and induced seismic events of societal significance. The Californië geothermal field in South Eastern Netherlands is one such project where concern for disruptive seismicity has stalled development. Evaluating seismic hazards of structurally-controlled geothermal systems must include a clear understanding of subsurface geometries, specifics of the current stress field, and rock properties at depth. At Californië, although considerable subsurface data is available, the extent and specific geometries of local faults and fault topologies, including paleo-fault structures, stratigraphic formations, as well as the stress field at reservoir depths are not all well understood. This study addresses these uncertainties with a probabilistic approach to three-dimensional structural and geomechanical modeling, qualifying primary observations of structural features and evidence of the in situ stress state with a cumulative measure of their uncertainties. A number of structural geometric realizations are derived from these probabilistic uncertainties and analysed using the finite element method to evaluate slip tendency, dilation tendency, and fracture susceptibility. The results of these calculations provide meaningful distributions for fault stability considering uncertainties of in situ stress, structural geometries, and frictional properties to inform development and operational parameters and enable a finer evaluation of seismic hazards and further geothermal development.
How to cite: Jones, A., Kruszewski, M., and Amann, F.: Investigating fault reactivation potential for the Californië geothermal field (the Netherlands) by addressing uncertainties with probabilistic modeling of structures and in situ stress., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19108, https://doi.org/10.5194/egusphere-egu25-19108, 2025.
we performed microseismicity detection and location using the deep learning method and obtained a high-precision earthquake catalog in the Changning gas field in China. It is found that the spatial and temporal characteristics of seismicity in the region are indicative of its correlation with industrial operations. The distribution of earthquakes at depth reflected variations in reservoir depth and provided valuable constraints on it. The horizontal layered distribution of earthquakes at depth is due to the formation of fracture surfaces from interconnected fractures near the reservoir during hydraulic fracturing (HF) operations, which clearly demonstrates how HF operations impact seismicity. We suggested that the horizontally layered distribution was driven by two fundamental mechanisms: reactivation of pre-existing faults during HF and injection of high-pressure fluids into the reservoir, leading to fracture creation. Several ML ≥4 earthquakes, which did not occur on well-defined seismogenic faults, may have been triggered by pore elastic coupling resulting from regional stress accumulation and fluid injection. Significantly, the ML 4.9 seismic sequence occurring at the basement indicates that fracking has reactivated and promoted pre-existing faults, highlighting the need for further investigation into potential seismic hazards in the region.
How to cite: Wen, Z. and Zhang, N.: The temporal and spatial evolution characteristics of induced seismicity in the Changning shale gas field based on dense array , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5018, https://doi.org/10.5194/egusphere-egu25-5018, 2025.
Induced seismicity following fluid injection in geothermal reservoirs presents significant challenges for risk mitigation and hazard assessment. While numerous studies have focused on seismicity during active injection phases, less attention has been given to the critical post-injection period when seismic activity gradually subsides. In this study, we systematically analyze post-injection seismic decay at three prominent geothermal sites—Soultz-sous-Forêts (France), Cooper Basin (Australia), and Basel (Switzerland)—leveraging high-resolution industrial datasets. We thank the EPOS TCS-AH platform and CDGP for providing the data used in this study. This work was supported by the European Union’s Horizon 2020 research and innovation program (DT-Geo, grant agreement No. 101058129).
Using the Modified Omori Model, we characterize seismic event density decay rates and evaluate their dependence on operational and hydraulic parameters, such as wellhead pressure dynamics, injection duration, hydraulic energy, and reservoir diffusivity. Our results highlight the pivotal influence of sustained wellhead pressure and its dissipation rate (γ) on seismic decay, where faster pressure dissipation promotes fault stabilization and leads to reduced seismic activity. Secondary influences include cumulative injection volume and hydraulic energy, which moderate fault reactivation processes. The corner time parameter (c), marking the onset of seismic decay, shows limited correlation with operational metrics, suggesting the importance of site-specific geological properties.
By comparing the Modified Omori Model with alternative decay models (e.g., Cut-off Power Law, Gamma, and Stretched Exponential), we demonstrate its robustness in capturing the temporal evolution of seismicity across diverse geological settings. These findings highlight the critical role of wellhead pressure management in reducing trailing seismic risks and offer actionable insights for optimizing geothermal operations. This work contributes to a deeper understanding of post-injection seismicity, advancing risk management strategies for sustainable geothermal energy development.
How to cite: Wang, Z., Lengliné, O., and Schmittbuhl, J.: Post-Injection Seismic Decay Dynamics at Geothermal Sites: Insights from Wellhead Pressure and Hydraulic Energy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6627, https://doi.org/10.5194/egusphere-egu25-6627, 2025.
Monitoring induced seismicity is an indispensable part of risk management during the creation and operation of enhanced geothermal systems. Due to the relative scarcity of manually labeled, informative datasets of induced seismicity, it can be challenging to evaluate the performance of monitoring tools ahead of time. We have created continuous synthetic seismic waveform data for an induced seismicity sequence at the Utah Frontier Observatory for Research in Geothermal Energy (FORGE). The data are based on a synthetic catalog that mimicks an injection-induced sequence at Utah FORGE and contains approximately 20 000 events occurring during 24 hours with the majority of events during the simulated hydraulic stimulation. Taking into account site-specific geology, induced event waveforms are computed using a spectral-element visco-elastic wave propagation solver and source-receiver reciprocity. Two types of seismic noise are added to create two subsets of test data: low-amplitude Gaussian noise and site-specific correlated noise. We test the retrieval of the known events from the continuous synthetic data using one real-time and one post-processing monitoring workflow based on SeisComP and MALMI (MAchine Learning aided earthquake MIgration location). The results illustrate reliability and shortcomings of the two monitoring tools. For example, depending on the monitoring tool, the noise conditions and the behaviour of the sequence (injection vs. post-injection), the rate of detected events ranges from approximately 20% to 100%. In addition to this benchmark, the dataset generation also serves as a rough feasibility study for a digital “twin” of wave propagation in an enhanced geothermal system. While uncertainties concerning the elastic medium and receiver coupling, as well as the time to availability of observed induced event data and interpretations are likely to pose challenges, the performance of the reciprocal wave propagation modeling strategy is satisfactory for incorporation into a “twin” if updates to the geologic structure are infrequent.
How to cite: Ermert, L., Shi, P., Lanza, F., Tuinstra, K., Ritz, V., Finger, C., Obermann, A., Rinaldi, A., and Wiemer, S.: A synthetic benchmark dataset for induced seismicity monitoring, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7125, https://doi.org/10.5194/egusphere-egu25-7125, 2025.
The Federal Seismic Survey at BGR routinely evaluates seismic events in Germany and neighbouring
countries on a daily basis. The results are supplemented by the outcomes of the seismological agencies of
the federal states of Germany and German universities and stored in an event database and in the German
earthquake catalogue, which is complete for earthquakes with magnitudes ML ≥ 2.
Furthermore, the events are classified as natural earthquakes, induced earthquakes, or explosions (mostly
quarry blasts). A considerable number of the events are induced earthquakes. They originate from stress
changes due to human activity in the subsurface. The main causes of the induced events are coal mining,
potash salt mining, natural gas extraction and geothermal energy.
We describe the characteristics of the associated seismicity for the different mining regions in Germany. In
contrast to natural seismicity characterized by long-term tectonic processes, the number and strength of
induced seismicity can be strongly dependent on rather short-term temporal and spatial changes following
the mining process.
The seismicity in coal mining regions, e.g., decreased coinciding with the shutdown of coal mining, whereas
seismic activity in geothermal or natural gas fields show different behavior, increasing or decreasing
depending on the location. Additionally, the latter both types of induced seismicity show remarkable
peculiarities in their temporal behavior. Seismic events still occur with a delay after a geothermal power plant
was shut down. Seismic activity can start even several years after the start of extraction in a new natural gas
field.
We show the temporal course of induced seismicity over the last 10 years in dependence on the distinct
extraction types, compare it with the previous decades and discuss the main features. In addition, we also
investigate the magnitude-frequency relationship and the energy release of the induced earthquakes. We
determine these parameters regarding their originators as well as in relation to those of natural earthquakes.
How to cite: Plenefisch, T., Bischoff, M., Gaebler, P., Hartmann, G., and Wegler, U.: Induced seismicity in Germany during the last decade - an overview and update, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9673, https://doi.org/10.5194/egusphere-egu25-9673, 2025.
Construction and cyclic operation of multi-cavern systems within salt pillars present notable geomechanical challenges, including subsidence due to cavern convergence, pressure interactions between caverns, leakage and induced seismicity. Monitoring stations in the northeast of the Netherlands have consistently reported small seismic events (local magnitudes ≥ -2), the underlying physics of which are poorly understood. As the operational activity in the salt domes is expected to scale up due to the prospects of underground hydrogen storage (UHS) in salt caverns, it is crucial to investigate the mechanisms underlying the observed seismic events. More importantly, it is essential to quantify the probability of induced seismic events due to the increase in UHS projects.
This study aims to assess the probability of induced seismicity associated with the prospect of large-scale hydrogen storage (UHS) plans. To this end, it is crucial to understand, analyse, and quantify the mechanisms behind induced seismicity observed due to the salt cavern leaching and cyclic storage operations within the Dutch salt domes. As a necessary bench-mark step for our study, it is essential to explain the occurrence of small-scale events for the existing caverns. We commence by constructing simplified yet meaningful simulation models, which include the basic characteristics of the salt formation, salt cavern, operational conditions, and the presence of structural features in the salt formation as well as in the over- and side-burden. Subsequently, the deformation evolution of the system is quantified and the impact of uncertainties on stress and deformation is assessed. The simulation model will be coupled to a seismogenic source model to compute the spatio-temporal development of the seismic activity in the model due to the deformation evolution.
How to cite: van den Ameele, N., Hajibeygi, P. dr. H., van Gent, Dr. H., and Muntendam-Bos, Dr. A.: Quantification of the probability of induced seismicity associated with large-scale underground hydrogen storage in Dutch salt formations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10194, https://doi.org/10.5194/egusphere-egu25-10194, 2025.
The heterogenous nature of geological formations is further complicated by natural and induced discontinuities such as fractures and faults. These geological features introduce a complex network of pathways and barriers that alter the local in-situ stresses as well as fluid flow dynamics. A comprehensive understanding of hydro-mechanical (HM) interactions during fluid injection experiments may provide insights into the effective manipulation of underground for energy extraction (e.g., hydraulic stimulation) as well as prediction and mitigation of induced seismicity in response to various stimulation techniques. Significant effort has been devoted to understand the rock-fluid interactions in energy contexts (e.g., shale gas, enhanced geothermal system) and earthquake seismology through various methodologies including laboratory studies, in-situ experiments and numerical simulations over the last decades. However, systematic studies of such interactions under in-situ conditions with natural heterogeneity require systematic manipulation of injection parameters in a well-characterized reservoir or underground research laboratory.
The BedrettoLab (Bedretto Underground Laboratory for Geosciences and Geoenergies) with a local overburden of over 1000 m, located in the Swiss Alps, is a suitable site for conducting such studies, as the rock volume has been well instrumented and characterized [Plenkers et al., 2023]. In a close collaboration between two running projects in BedrettoLab, i.e., VALTER (Validating of Technologies for Reservoir Engineering) and FEAR (Fault Activation and Earthquake Rupture), a series of controlled hydraulic stimulations were conducted where various HM pre-conditioning steps were included (or left out) in the injection protocol. The main objective of the HM pre-conditioning was to understand and control microseismicity by pre-determining the pressurized patch on the fault/fracture volume via the injection protocol prior to the main injection. The installed monitoring system captured ongoing HM processes during each hydraulic stimulation, enabling systematic testing of these pre-conditioning hypothesis across various fractures. In the next step, similar protocols were applied to the first stimulation experiment as part of the project which provided a comprehensive insight of the HM and seismogenic characteristics of the stimulated fault, in response to pre-conditioning.
How to cite: Jalali, M., Gischig, V., Selvadurai, P., Spagnuolo, E., Meier, M.-A., Dal Zilio, L., Rosskopf, M., Obermann, A., Rinaldi, A. P., Gholizadeh Doonechaly, N., Bröker, K., Osten, J., Hertrich, M., Maurer, H., Giardini, D., Wiemer, S., Cocco, M., and Amann, F. and the FEAR Team: Hydraulic Stimulations with Hydro-Mechanical Pre-Conditioning at the BedrettoLab, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17247, https://doi.org/10.5194/egusphere-egu25-17247, 2025.
The Baihetan Hydropower Station, located on the eastern margin of the Tibetan Plateau, is the world's second-largest hydropower station in terms of installed capacity. The 289-meter-high dam will create a massive reservoir with a storage capacity of 20.6 billion cubic meters upstream of the Jinsha River. On April 6, 2021, the Baihetan Reservoir began its initial impoundment, leading to significant seismic activity at the intersection of the Xiaojiang, Zemuhe, and Daliangshan fault zones. These earthquakes were characterized by shallow focal depths and a general distribution along the reservoir area, indicating reservoir-induced seismicity. During the initial impoundment of the Baihetan Reservoir, two notable earthquakes occurred within the Tibetan Plateau, the Yangbi MS 6.4 earthquake and the Maduo MS 7.4 earthquake, with an interval of less than five hours between them.
This study utilizes data from a dense seismic array deployed in the Baihetan Reservoir area to analyze the remote dynamic triggering effects of these two earthquakes. Preliminary works indicate that the surface waves from the Yangbi MS 6.4 earthquake, which was approximately 330 km away, did not trigger any small earthquakes in the Baihetan Reservoir area, and there was no significant increase in microseismic activity within four hours after the earthquake. In contrast, the surface waves from the Maduo MS 7.4 earthquake, which was about 920 km away, triggered multiple small earthquakes when they reached the Baihetan Reservoir area. Additionally, precise earthquake relocations reveal the heterogeneous distribution of critical stress states in the Baihetan Reservoir area due to the impoundment process. These results provide insights into the mechanisms of reservoir-induced seismicity and the potential for remote dynamic triggering in the region.
How to cite: Liu, Z., Wu, T., and He, X.: Remote dynamic triggering of reservoir-induced seismicity during the initial impoundment of the Baihetan Reservoir, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17304, https://doi.org/10.5194/egusphere-egu25-17304, 2025.
The global development of Enhanced Geothermal Systems (EGS) and the increasing related occurrence of induced seismicity are topics of growing interest for the scientific community. One of the most recent EGS developments is in the Gonghe Basin, located in the northeastern Quinghai-Tibetan Plateau in China. The project is considered one of the most promising Hot Dry Rock (HDR) resources in the country due to the high temperature detected while drilling the first well in 2017 (236°C at a depth of 3705 m).
A surface seismic network of 20 three-component seismometers monitored the area around the wells GH01, GH02, and GH03 during the June – October 2021 injection and circulation phases. We used a beamforming method to detect and locate earthquakes. The beamforming process significantly improved the number of events detected, with over 10,000 detections (whereas previous research had identified roughly 2,600 events using an automated phase-picker for detections). The largest event had a magnitude of ML 3.2, with the smallest events having magnitudes smaller than ML -1. The increased event detection produced by the beamforming is fundamental for enhanced imaging of the faults and fractures activated by the geothermal stimulations. We compare the beamforming locations with those produced by manual phase picking for the largest events with ML > 0.7.
Further seismological analysis has included analysis of shear wave splitting (SWS) phenomena, to understand the development of anisotropy in the reservoir during and after the injection procedures. Our results show that the fast S-wave polarization have a NE-SW orientation, congruent with the orientation of the maximum horizontal principal stress, characterized by a direction of NE55°. However, variations into the orientation are present at some stations, which could indicate additional geological complexity within the area.
How to cite: Bressan, S., Verdon, J., and Zhang, H.: Characterization of induced micro seismicity at the Gonghe geothermal project during the 2021 injection phase, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17271, https://doi.org/10.5194/egusphere-egu25-17271, 2025.
Identification of seismogenic zones in geothermal fields undergoing active fluid injection is an important issue for seismic hazard assessment in such destinations. It is well known that subsurface discontinuities can be successfully imaged using multiplets, i.e. seismic events with very similar waveforms. Very promising results of this method were obtained using the dataset from Prati-9 and Prati-29 injection wells at The Geysers geothermal field. With the use of multiplet analysis followed by double-difference relocation we imaged three fractures and one fault within the reservoir and described their different seismic response to injection.
In this work we present the current results of multiplet identification followed by double-difference relocation in two other geothermal sites: (1) Helsinki geothermal site (Finland), and (2) Coso geothermal field (California). The mentioned geothermal sites exhibit very different geological conditions. Helsinki site is a typical example of geothermal stimulation of crystalline Precambrian basement rocks in the area of very low background seismicity. On the contrary, Coso geothermal field is located in tectonically active volcanic area cut with a complex system of faults. Moreover, we extend the multiplet analysis performed in the area of Prati-9 and Prati-29 injection wells at The Geysers geothermal field by searching for multiplets in various frequency ranges. In this way seismic events from broader magnitude range can be included in the following relocation procedure. The multiplets identified within each frequency range are relocated separately. At the end, obtained images are stacked together using common reference events.
Our results confirm that relative relocation of similar seismic events with double-difference method can be successfully applied for the identification of seismogenic structures in geothermal areas exhibiting very different geological and tectonic complexity.
This research was supported by research project no. 2022/45/N/ST10/02172, funded by the National Science Centre, Poland, under agreement no. UMO-2022/45/N/ST10/02172. This work was also partially supported by a subsidy from the Polish Ministry of Education and Science for the Institute of Geophysics, Polish Academy of Sciences. This research was supported in part by PLGrid Infrastructure.
How to cite: Staszek, M., Rudziński, Ł., and Wiszniowski, J.: Multiplets as a tool for identification of seismogenic structures at various geothermal fields, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18119, https://doi.org/10.5194/egusphere-egu25-18119, 2025.
To determine the source characteristics of mining-induced earthquakes, the corner frequency fc, rupture radius r, seismic moment M0, radiated seismic energy Es, and stress drop Δσ of 80 micro-earthquakes with 1.0≤ML≤3.3 in the Datong coal mine were calculated based on waveform records from the regional digital seismic network. The Scaling relationships between these parameters and M0 were studied, and the reasons for the lower levels of corner frequency and stress drop in mining-induced seismicity were analyzed. The results show that the displacement spectrum of the source of mining-induced earthquakes in the Datong coal mining is consistent with the Brune model ω-2 attenuation pattern. Using this ω-2 model, the source parameters of micro-earthquakes in the Datong coal mine were estimated. The fc ranges mainly from 0.82 to 4.64 Hz, the r ranges from 67.89 to 382.65 m, and the Δσ from 0.03 to 0.85 MPa. The M0 estimated from the zero frequency limit ranges from 5.85e+10 to 7.66e+13 Nm, and the Es ranges from 7.34e+4 to 7.07e+8 J. With the increase of M0, the source parameters of r, Δσ, and Es show an increasing trend, while the fc decreases gradually, exhibiting characteristics similar to tectonic earthquakes. Mining-induced earthquakes in the Datong coal mining area have lower corner frequencies and stress drop levels than tectonic earthquakes. This is mainly due to the artificial alteration of the initially stable geological structure and stress state during mining. This leads to deformation and micro-fracturing of the coal and rock mass in the roof and floor, approaching or reaching a critical, unstable state. With the continuous mining operation, mining-induced earthquakes occur in a lower-stress environment under the multiple coupling effects of the self-weight stress of the coal and rock mass and mining-induced stress disturbance.
How to cite: Li, L. and Liu, J.: Source Parameters and Scaling Relationships for Mining-induced Seismicity in the Datong Coal, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17776, https://doi.org/10.5194/egusphere-egu25-17776, 2025.
