Tomáš Fischer

Charles University

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Josef Horálek

Czech Academy of Sciences

Josef Vlček

Charles University

Sebastian Hainzl

Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

Pavla Hrubcová

Czech Academy of Sciences, Institute of Geophysics

Torsten Dahm

Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

Jana Doubravová

Czech Academy of Sciences, Institute of Geophysics

Martin Bachura

Czech Academy of Sciences, Institute of Geophysics

ÞÁ

Þorbjörg Ágústsdóttir

Iceland GeoSurvey

EÁ

Egill Árni Guðnason

Iceland GeoSurvey

Jan Michálek

University of Bergen

Cooperative Institutions

Charles University

Czech Academy of Sciences

Czech Academy of Sciences, Institute of Geophysics

Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

University of Potsdam

University of Iceland

Czech Geological Survey

Czech Academy of Sciences, Institute of Rock Structure and Mechanics

Institute of Geophysics

Geophysical Division of the Earth Science Institute of the Slovak Academy of Sciences

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Review of manuscript Event couple spectral ratio Q method for earthquake clusters: application to North-West Bohemia by Kriegerowski et al., submitted to Solid Earth.

Tomáš Fischer

Solid earth

10.5194/se-2018-87-rc2

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On the Move: 2023 Observations on Real Time Graben Formation, Grindavík, Iceland

Geophysical Research Letters (2024)

Gregory P. De Pascale Tomáš Fischer William Moreland H. Geirsson Pavla Hrubcová

Abstract Grabens, or valleys formed during extensional tectonic events, are common but rarely observed during formation. In November 2023, inelastic surface deformation formed abruptly along Iceland's plate boundary in Grindavík. We documented graben formation in real‐time through satellite mapping (InSAR), seismicity, GNSS data, repeated lidar surveys, and field mapping. Five normal faults and ∼12 fissures ruptured the surface delineating two grabens separated by a horst, a context not present in other contemporary case studies. The graben normal faults slipped rapidly (over hours) and maximum surface motions coincided with the occurrence of turbulent seismic swarms in both space and time. Although 3 eruptions took place ∼15 km northeast of Grindavík from 2021 to 2023, attributed to magma intrusions (i.e., dikes), none of these also formed grabens. Thus, the Grindavík grabens shows evidence for tectonic origins. Real‐time monitoring of these phenomena provide insight into graben formation on Earth and potentially on other planets.

Horst and graben

Dike

Horst

10.1029/2024gl110150

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Citations (1)

Temperature Fluctuations underneath the Ice in Diamond Lake, Minnesota

EGU General Assembly Conference Abstracts (2012)

G. Kletetschka Tomáš Fischer Jiří Mls

Source

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Geophysical evidence of the Eastern Marginal Fault of the Cheb Basin (Czech Republic)

Studia Geophysica et Geodaetica (2018)

Vratislav Blecha Tomáš Fischer Petr Tábořík Jan Vilhem Radek Klanica

Bedrock

Geophysical survey

Electrical Resistivity Tomography

Seismic refraction

10.1007/s11200-017-0452-9

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Citations (16)

Attenuation of seismic waves obtained by coda waves analysis in the West Bohemia earthquake swarm region

EGUGA (2014)

Martin Bachura Tomáš Fischer

Coda

Source

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The Growth of Earthquake Clusters

Frontiers in Earth Science (2021)

Tomáš Fischer Sebastian Hainzl

Migration of hypocenters is a common attribute of induced injection seismicity and of earthquake swarms, which distinguishes them from aftershock sequences. Spreading of the triggering front is often examined by fitting the time dependence of hypocenter distances from the origin by the pore pressure diffusion model. The earthquake migration patterns however often exhibit not only spreading envelopes but also fast-growing streaks embedded in the overall migration trends. We review the observed migration patterns and show that in the case of earthquake-driven migration, where the new ruptures are triggered at the edge of previous ruptures, it is more suitable to examine the cluster growth as a function of the event index instead of time. We propose a model that relates the speed of seismicity spreading to the average rupture area and the effective magnitude of the hypocenter cluster. Application of the model to selected linearly growing clusters of the 2008 West Bohemia swarm gives an almost linear increase of the measured total rupture area with the event index, which fits the proposed model. This is confirmed by a self-similar scaling of the average rupture area with the effective magnitude for stress drops ranging from 0.1 to 1 MPa. The relatively small stress drop level indicates the presence of voids along the fault plane and a possible role of aseismic deformation.

Hypocenter

Fault plane

10.3389/feart.2021.638336

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Citations (28)

Detection of repeated hydraulic fracturing (out-of-zone growth) by microseismic monitoring

The Leading Edge (2006)

Leo Eisner Tomáš Fischer J. H. Le Calvez

Hydraulic fracture treatments are commonly carried out in several space- and time-staggered stages which are designed to stimulate isolated segments of a reservoir (i.e., multistage fracturing). However, repeated hydraulic fracturing of reservoir segments fractured in previous stages is commonly observed. In multistage fracturing this problem is also known as out-of-zone or out-of-pay growth, and we shall call it cross-stage fracturing in this article. Cross-stage fracturing can be detected by automated identification of multiplets, i.e., microseismic events with similar source mechanisms and nearly identical location. We applied multiplet identification to detect cross-stage fracturing on two hydraulic fracture monitoring data sets (Canyon Sand and Barnett Shale formations) one of which is described in this paper. We verified this detection method with the initial microseismic events locations. Cross-stage fracturing was detected only a few minutes after the first microseismic events had been detected an...

Microseism

10.1190/1.2202655

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Citations (36)

Are the recurring earthquake swarms in West-Bohemia rain triggered?

Josef Vlček Roman Beránek Tomáš Fischer

In past decades, a significant effort was spent to find the origin of recurring earthquake swarms in West-Bohemia/Vogtland. Widespread understanding accepts that crustal fluids migration along the fault zones is responsible for earthquake triggering in this area. Recently, a new model was suggested, which tests the hypothesis whether the diffusion of hydraulically induced pore pressure could be a valid trigger mechanism. In this approach the precipitation signal was transformed by diffusion equation to the hypocenter depth and statistically compared with the earthquake occurrence in time and concluded that at least 19% of the seismicity could have been triggered by rain.&#160;In our study we apply a different approach to verify the validity of these results. We use two types of rain signal on the input which is compared with the time series of earthquake weekly rate for the past 25 years. To remove the strong episodic character of the swarm seismicity we use a declustered seismic catalog, which is characteristic by almost continuous seismic activity.The rain signal is represented first by the precipitation data and second by the water level data in the Horka reservoir, which is located above the main focal zone of Nov&#253; Kostel. We test the possible relation to the earthquake swarm activity by cross correlating both the rain signal types and the seismicity rate. To amplify the possible seasonal periodicity of the data we stacked the explored time series data (precipitation, water level and seismic activity) according to their occurrence date in a single year. The results show that in any of the input data and seismicity do not correlate.&#160;In the next step, we tested the possible (annual) periodicity of the data in question by the singular spectral analysis (SSA), which is a sensitive method to identify possible periodic signals in the presence of noise. While the water level data showed a striking peak for the period of 1 year, any indication of annual periodicity was never found in the seismicity data. Accordingly, we conclude that our analysis has shown no influence of the precipitation or the water level fluctuations in the Horka dam to the earthquake swarm activity in West Bohemia/Vogtland.

Hypocenter

SIGNAL (programming language)

Earthquake prediction

Normal fault

10.5194/egusphere-egu21-14986

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Geological interpretation of gravity profiles through the Karlovy Vary granite massif (Czech Republic)

Studia Geophysica et Geodaetica (2009)

Vratislav Blecha Miroslav Štemprok Tomáš Fischer

Massif

Outcrop