Patricia Martínez‐Garzón

Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

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Marco Bohnhoff

Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

Grzegorz Kwiatek

Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

Georg Dresen

Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

Yehuda Ben‐Zion

Southern California University for Professional Studies

Murat Nurlu

Dirk Becker

Praxis

Christopher Wollin

Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

Stephan Bentz

Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

Virginie Durand

Centre National de la Recherche Scientifique

Gregory C. Beroza

Stanford University

Cooperative Institutions

Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

University of Potsdam

Centre National de la Recherche Scientifique

Istituto Nazionale di Geofisica e Vulcanologia

Stanford University

Ruhr University Bochum

Centre de Géosciences

Technische Universität Berlin

Geriatrische Gesundheitszentren

United States Geological Survey

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Low-frequency tremor-like episodes before the 2023 MW 7.8 Türkiye earthquake linked to cement quarrying

Scientific Reports (2025)

Zahra Zali Patricia Martínez‐Garzón Grzegorz Kwiatek Sebastián Núñez-Jara Gregory C. Beroza

Spectrogram

Plucking

10.1038/s41598-025-88381-x

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Moment tensors of waste-water disposal induced seismicity in Southern Kansas.

AGU Fall Meeting Abstracts (2019)

Amandine Amemoutou Patricia Martínez‐Garzón Grzegorz Kwiatek J. L. Rubinstein Marco Bohnhoff

waste disposal

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Fault-Zone Maturity Defines Maximum Earthquake Magnitude: The case of the North Anatolian Fault Zone

EGU General Assembly Conference Abstracts (2015)

Marco Bohnhoff Fatih Bulut Eva Stierle Patricia Martínez‐Garzón Yehuda Ben‐Zion

North Anatolian Fault

Earthquake magnitude

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Slow strain release along the eastern Marmara seismic gap offshore Istanbul in conjunction with enhanced local seismic moment release

AGU Fall Meeting Abstracts (2018)

Patricia Martínez‐Garzón Marco Bohnhoff D. Mencin Grzegorz Kwiatek Georg Dresen

Conjunction (astronomy)

Strain (injury)

Seismic moment

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Insights Into Complex Subdecimeter Fracturing Processes Occurring During a Water Injection Experiment at Depth in Äspö Hard Rock Laboratory, Sweden

Journal of Geophysical Research Solid Earth (2018)

Grzegorz Kwiatek Patricia Martínez‐Garzón Katrin Plenkers Maria Leonhardt Arno Zang

Abstract We investigate the source characteristics of picoseismicity ( M w < −2) recorded during a hydraulic fracturing in situ experiment performed in the underground Äspö Hard Rock Laboratory, Sweden. The experiment consisted of six stimulations driven by three different water injection schemes and was performed inside a 28‐m‐long, horizontal borehole located at 410‐m depth. The fracturing processes were monitored with a variety of seismic networks including broadband seismometers, geophones, high‐frequency accelerometers, and acoustic emission sensors thereby covering a wide frequency band between 0.01 and 100,000 Hz. Here we study the high‐frequency signals with dominant frequencies exceeding 1000 Hz. The combined seismic network allowed for detection and detailed analysis of 196 small‐scale seismic events with moment magnitudes M W < −3.5 (source sizes of decimeter scale) that occurred solely during the stimulations and shortly after. The double‐difference relocated hypocenter catalog as well as source parameters were used to study the physical characteristics of the induced seismicity and then compared to the stimulation parameters. We observe a spatiotemporal migration of the picoseismic events away and toward the injection intervals in direct correlation with changes in the hydraulic energy (product of fluid injection pressure and injection rate). We find that the total radiated seismic energy is extremely low with respect to the product of injected fluid volume and pressure (hydraulic energy). The radiated seismic energy correlates well with the hydraulic energy rate. The obtained fault plane solutions for particularly well‐characterized events signify the reactivation of preexisting rock defects under influence of increased pore fluid pressure on fault plane orientations in good correspondence with the local stress field orientation.

Geophone

Seismometer

Passive seismic

Hypocenter

Seismic moment

Microseism

10.1029/2017jb014715

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Citations (53)

Analysis of Microseismicity Framing M_L > 2.5 Earthquakes at The Geysers Geothermal Field, California

Journal of Geophysical Research Solid Earth (2019)

Stephan Bentz Patricia Martínez‐Garzón Grzegorz Kwiatek Georg Dresen Marco Bohnhoff

Abstract Preparatory mechanisms accompanying or leading to nucleation of larger earthquakes have been observed at both laboratory and field scales, but conditions favoring the occurrence of observable preparatory processes are still largely unknown. In particular, it remains a matter of debate why some earthquakes occur spontaneously without noticeable precursors as opposed to events that are preceded by an extended failure process. In this study, we have generated new high‐resolution seismicity catalogs framing the occurrence of 20 M L > 2.5 earthquakes at The Geysers geothermal field in California. To this end, a seismicity catalog of the 11 days framing each large event was created. We selected 20 sequences sampling different hypocentral depths and hydraulic conditions within the field. Seismic activity and magnitude frequency distributions displayed by the different earthquake sequences are correlated with their location within the reservoir. Sequences located in the northwestern part of the reservoir show overall increased seismic activity and low b values, while the southeastern part is dominated by decreased seismic activity and higher b values. Periods of high injection coincide with high b values and vice versa. These observations potentially reflect varying differential and mean stresses and damage of the reservoir rocks across the field. About 50% of analyzed sequences exhibit no change in seismicity rate in response to the large main event. However, we find complex waveforms at the onset of the main earthquake, suggesting that small ruptures spontaneously grow into or trigger larger events.

Microseism

Framing (construction)

10.1029/2019jb017716

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Citations (7)

Microearthquakes preceding a M4.2 Earthquake Offshore Istanbul

Scientific Reports (2018)

P. E. Malin Marco Bohnhoff Felix Blümle Georg Dresen Patricia Martínez‐Garzón

A primary hurdle in observing small foreshocks is the detection-limit of most seismic networks, which is typically about magnitude M1-1.5. We show that a start-up test of a borehole-based seismic network with a much lower detection limit overcame this problem for an Mw4.2 earthquake. This earthquake occurred offshore of Istanbul, Turkey, on a fault system that is likely to rupture in an M > 7 event in the coming decades. In the three days before and two after, a total of 62 or more earthquakes, including at least 18 foreshocks, came from the mainshock source area. The signal similarity of the foreshocks shows a clear increase during the hours before the Mw4.2 mainshock. Similar foreshock sequences have recently been reported for a few well monitored M > 7 plate-boundary earthquakes. The sequence surrounding the Mw4.2 gives the impression of stochastic failures that ended up interactively unloading stress concentrations. The Mw4.2 mainshock then resulted from the accumulated release of significantly smaller events, as suggested by other field and laboratory studies.

Earthquake prediction

10.1038/s41598-018-34563-9

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Citations (30)

Sea Level Changes Affect Seismicity Rates in a Hydrothermal System Near Istanbul

Geophysical Research Letters (2023)

Patricia Martínez‐Garzón Gregory C. Beroza Gian Maria Bocchini Marco Bohnhoff

Abstract Small stress changes such as those from sea level fluctuations can be large enough to trigger earthquakes. If small and large earthquakes initiate similarly, high‐resolution catalogs with low detection thresholds are best suited to illuminate such processes. Below the Sea of Marmara section of the North Anatolian Fault, a segment of 150 km is late in its seismic cycle. We generated high‐resolution seismicity catalogs for a hydrothermal region in the eastern Sea of Marmara employing AI‐based and template matching techniques to investigate the link between sea level fluctuations and seismicity over 6 months. All high resolution catalogs show that local seismicity rates are larger during time periods shortly after local minima of sea level, when it is already rising. Local strainmeters indicate that seismicity is promoted when the ratio of differential to areal strain is the largest. The strain changes from sea level variations, on the order of 30–300 nstrain, are sufficient to promote seismicity.

10.1029/2022gl101258

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A refined methodology for stress inversions of earthquake focal mechanisms

Journal of Geophysical Research Solid Earth (2016)

Patricia Martínez‐Garzón Yehuda Ben‐Zion Niloufar Abolfathian Grzegorz Kwiatek Marco Bohnhoff

Abstract We develop an improved methodology for reliable high‐resolution inversions of focal mechanisms to background stress field orientation and stress ratio R in two or three dimensions. The earthquake catalog is declustered to remove events likely affected strongly by local stress interactions rather than reflecting the large‐scale background stress field. The declustered data are discretized with the k ‐means algorithm into groups containing a number of focal mechanisms between a minimum number N min and 2 N min . Synthetic tests indicate that N min ≈ 30 provides stable inversion results under different stress regimes and noise conditions when R ≈ 0.5, while N min ≈ 45 is needed for R near 0 or 1. Additional synthetic tests compare the performance of selecting the fault plane of each focal mechanism using (a) the plane with lowest misfit angle between the slip vector from the focal mechanism and shear traction from the stress tensor and (b) the plane with highest instability coefficient representing proximity to the optimally oriented fault for given stress field and friction coefficient. The instability criterion is found to provide more accurate inversion results under all tested stress regimes, stress ratios, and noise conditions. The refined inversion methodology combines selecting fault planes using the instability criterion iteratively with a damped simultaneous inversion of different focal mechanism groups. Results characterizing neighborhoods of discretized domains merged during the damped inversion provide high‐resolution information independent of the discretization. Some aspects of the methodology are illustrated with focal mechanism data from the San Jacinto Fault Zone in Southern California.

Focal mechanism

Fault plane

Stress field

10.1002/2016jb013493

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Citations (91)

Complex multi-scale preparatory processes of stick-slip events on rough laboratory faults

Authorea (Authorea) (2023)

Grzegorz Kwiatek Patricia Martínez‐Garzón Thomas Goebel Marco Bohnhoff Yehuda Ben‐Zion

We discuss data of laboratory stick-slip experiments on Westerly Granite samples performed at elevated confining pressure and constant displacement rate on rough pre-fractured faults. The experiments produced complex slip patterns including fast and slow ruptures with large and small fault slips, as well as failure events on the fault surface producing acoustic emission bursts without externally-detectable stress drop. Preparatory processes leading to large slips were tracked with an ensemble of ten seismo-mechanical and statistical parameters characterizing local and global damage and stress evolution, localization and clustering processes, as well as event interactions. We decompose observable complex spatio-temporal trends in AE-derived seismic characteristics identifying effects of persistent and evolving fault roughness at different length scales, multi-scale damage, and local stress evolution approaching large events. The observed trends highlight localization processes on different spatial and temporal scales. The preparatory process of large slip events is facilitated by smaller events marked by confined bursts of AE activity that collectively prepare the fault surface for a system-wide failure by conditioning the large-scale stress field. Our results provide a set of reliable, physics-based characteristics of processes leading to large failure events that may allow for improved earthquake forecasting along natural faults.

Acoustic Emission

Stress field

10.22541/essoar.169447455.58529925/v1

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Citations (2)