Faulting style and stress field investigations for swarm earthquakes in NE Baveria/Germany – the transition between Vogtland/NW-Bohemia and the KTB-site

Seht, M. Ibs-von; Plenefisch, Thomas; Schmedes, E.

doi:10.1007/s10950-005-9008-5

Cited by 7 publications

(3 citation statements)

References 25 publications

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“…In particular, the orientation of the maximum principal stress determined from the swarm earthquakes ranges from 130° to 142° (Vavryčuk, 2000;Havíř, 2000;Wirth et al, 2000). This local-scale stress field is quite consistent with the regional stress field (145°) in Central Europe (Müller et al, 1992;Seht et al, 2006). Schenk's et al (2009) "antithetic" stress model however requires different stress fields on the large and small scale.…”

supporting

confidence: 82%

Comment on the “Geodynamic pattern of the West Bohemia region based on permanent GPS measurements” by V. Schenk, Z. Schenková and Z. Jechumtálová (Stud. Geophys. Geod., 53(2009), 329–341)

Fischer

Horálek

2009

Stud Geophys Geod

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Schenk et al. (2009) present in their paper the results of permanent GPS observations in the earthquake-swarm region of West Bohemia. The authors use six GPS stations operating in the area of interest for the period of the past two to five years. Four stations are situated in the northern seismoactive part of the area (see Schenk et al., 2009, Fig. 3) and two are located about 100 km SSE. The Bernese GPS Software version 5.0 is used to process the data and the results are presented in the form of time series (Schenk et al., 2009, Fig. 2) showing the three-component site positions of individual stations with respect to the ITRS coordinate system (e.g. Larson et al., 1997). In the next step linear regression is used to obtain site velocities and their errors. All components show very similar values of about 20 mm/year for the east component; 14 mm/year for the north component and −2 mm/year for the vertical component. The velocities are then corrected for their medians resulting in relative values ranging about 1 mm/year. Finally, the motion of the northern stations is related to the Mariánské Lázně Fault (MLF) and a dextral horizontal velocity of 0.7 ± 0.1 mm/year along this fault is obtained. Additionally an extension of 0.8 ± 0.2 mm/year is found in the area of Mariánské Lázně fault.These findings are in contradiction with the focal mechanisms of swarm earthquakes in the Nový Kostel focal zone in the proximity of the MLF: the greatest part of them (the strongest swarms 1985/86, 2000 and 2008) show sinistral strike-slip mechanisms with almost N-S oriented fault plane (strike angles ~ 165°) which agrees well with the geometry of hypocenter clusters (Hainzl and Fischer, 2002;Fischer and Horálek, 2005). Schenk et al. (2009) are aware of the former fact, and to explain the discrepancy they argue that the sinistral movements correspond well with their findings of extension in the area and propose a model of "antithetic" stress state, combining the dextral movements in the large-scale and sinistral and extensional movements in the small-scale (see Schenk et al., 2009, Fig. 5).We want to comment here in particular the relevancy of the proposed model of antithetic stress state, which aims to explain the inconsistent sense of the movement at the surface obtained from GPS measurements and in depth obtained from the focal mechanisms of earthquakes. The basis of our approach is requirement for consistency of the stress field, orientation of the fault planes and sense of movement on these planes. In other words, we argue that the slip direction of the faults is controlled by the orientation of the main stress component. This is precisely the case of the Nový Kostel focal zone where

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confidence: 82%

Comment on the “Geodynamic pattern of the West Bohemia region based on permanent GPS measurements” by V. Schenk, Z. Schenková and Z. Jechumtálová (Stud. Geophys. Geod., 53(2009), 329–341)

Fischer

Horálek

2009

Stud Geophys Geod

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“…[8] To obtain site movement velocities, the data from these five network sites, three EPN permanent stations (BORI, PENC, and ZIMM), and the surrounding GNSS permanent stations (KYNS, LUBY, MARJ, POUS) of the GEONAS network [Schenk et al, 2010a] were obtained, and the solution for each GPS observation day was computed using Bernese GPS v.5 software [Hugentobler et al, 2005]. The following complementary data were applied during processing: (a) the precise satellite orbits, the satellite clock data, and the Earth's rotation parameters obtained from the Centre for Orbit Determination in Europe (CODE), Bern; (b) the antenna phase center characteristics obtained from the Geosciences Research Division of the U.S. National Geodetic Survey; (c) the stochastic model of ionosphere GLOBAL (CODgpswd.ION) used for estimating the ionospheric correction; (d) the linear combinations of L3 observations (ionosphere free); (e) the Quasi Ionosphere Free Strategy for ambiguity resolution; and (f ) the DRY NIELL atmospheric model for estimating the tropospheric correction.…”

Section: The Geological Structure Of the Areamentioning

confidence: 99%

Crustal deformations in the epicentral area of the West Bohemia 2008 earthquake swarm in central Europe

et al. 2012

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[1] In West Bohemia, central Europe, during October 2008 an earthquake swarm of 25,000 shocks with a maximum event of M L $ 3.7-3.8 occurred at depths of 7-11 km. In 2007, annual GPS campaigns were launched. During the co-seismic phase, displacements of a few centimeters were detected at GPS sites. Maximum displacement was revealed at the KOPA site, which subsided by 167 mm. The epicentral area is covered by eluvium of 4-10 m thick, and is located in undulating pastures and well-forested valleys where visible surface soil effects could not be observed. To test possible fault manifestations, rough geomorphologic, geoelectric, and geochemical surveys were performed. GPS and seismic data, with geologic materials, were used to build a forward model for surface displacements, crustal deformations, and shear and normal stress fields. The fields enabled us to better determine crustal deformations and stresses that appeared within the seismic cycle, during the pre-, co-, and post-seismic phases. During the co-seismic phase, modeled fault motions along N-S faults located within the epicentral zone reached 0.6-1 mm/day. Possible structural block rotations were comprised of these motions. A dominant role for stress accumulation, release, and relaxation was assigned to the Mariánské Lázně fault zone and the Nový Kostel zone. Strain loads slowly, and when local PT conditions with an action of deep magmatic fluids reach instability, the strain is released and stress balancing occurs. The process leads to the reversible motions known for silent earthquakes. A forward crustal deformation model for West Bohemia is also presented within.

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“…It is worth mentioning that Havíř in the west part of Fig. Seht et al (2006) axes from North to South (Seht et al, 2006, Fig. Seht et al (2006) axes from North to South (Seht et al, 2006, Fig.…”

Section: Application Of Fault Plane Solutionsmentioning

confidence: 99%

Reply to comment of T. Fischer and J. Horálek on “Geodynamic pattern of the West Bohemia region based on permanent GPS measurements” by V. Schenk, Z. Schenková and Z. Jechumtálová

Schenk¹,

Schenková²,

Jechumtálová³

2009

Stud Geophys Geod

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Faulting style and stress field investigations for swarm earthquakes in NE Baveria/Germany – the transition between Vogtland/NW-Bohemia and the KTB-site

Cited by 7 publications

References 25 publications

Comment on the “Geodynamic pattern of the West Bohemia region based on permanent GPS measurements” by V. Schenk, Z. Schenková and Z. Jechumtálová (Stud. Geophys. Geod., 53(2009), 329–341)

Comment on the “Geodynamic pattern of the West Bohemia region based on permanent GPS measurements” by V. Schenk, Z. Schenková and Z. Jechumtálová (Stud. Geophys. Geod., 53(2009), 329–341)

Crustal deformations in the epicentral area of the West Bohemia 2008 earthquake swarm in central Europe

Reply to comment of T. Fischer and J. Horálek on “Geodynamic pattern of the West Bohemia region based on permanent GPS measurements” by V. Schenk, Z. Schenková and Z. Jechumtálová

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