Faulting style and stress field investigations for swarm earthquakes in NE Baveria/Germany – the transition between Vogtland/NW-Bohemia and the KTB-site
- 71 Downloads
A seismicity and stress field analysis of a region in NE Bavaria reveals a complex picture of seismic dislocation. The magnitudes are generally low, the strongest event recorded had a magnitude of 2.3. In the southern part of the area investigated, earthquakes occur very rarely. During the observation period of approximately four years, only four events, two of them forming a doublet, were recorded. Hypocentral depths in the southern part are considerably great (15 to 17 km) and indicate a mafic lower crust. The seismicity of the Marktredwitz area, located in the western extension of the Eger rift, is dominated by earthquake swarms that are strongly clustered in space and time. The swarms occurred at depths between 10 and 14 km. Precise relative relocations show clear planar arrangements of the hypocentres and enable to identify the orientation of active fault planes. A comparison of the structural and geomorphological settings reveals major similarities in the occurrence of earthquake swarms compared to the situation in the bordering Vogtland/NW-Bohemia swarm area.
Focal mechanisms cover a wide range of faulting styles. Normal fault, strike slip and reverse fault mechanisms as well as movements along sub-horizontal planes were found. The focal mechanisms were used to invert for the stress field. The inversion results reveal an ambiguity for the state of stress in the area of investigation and allow two different interpretations: A clockwise rotation of the stress field from North to South as well as a predominance of two slightly different stress regimes are possibilities.
Keywordsfocal mechanisms seismicity stress field swarm earthquakes Vogtland/NW-Bohemia
Unable to display preview. Download preview PDF.
- Bohnhoff, M., Baisch, S. and Harjes, H., 2004. Fault mechanisms of induced seismicity at the superdeep German Continental Deep Drilling Program (KTB) borehole and their relation to fault structure and stress field. J. Geophys. Res., 109, B02309, doi:10.1029/2003JB002528.Google Scholar
- DEKORP Research Group, 1988. Results of the DEKORP 4/KTB Oberpfalz deep seismic reflection investigations. J. Geophys. 62, 69–101.Google Scholar
- Gebrande, H., Bopp, M., Neurieder, P. and Schmidt, T., 1989. Crustal structure in the surroundings of the KTB drill site as derived from refraction and wide-angle seismic observations, in R. Emmermann und J. Wohlenberg (eds.), The German Continental Deep drilling Program (KTB), Springer Verlag, 151–176.Google Scholar
- Jost, M., Büsselberg, T., Jost, O., and Harjes, H.-P., 1998. Source parameters of injection-induced micro-earthquakes at 9 km depth at the KTB drilling site, Germany. Bull. Seism. Soc. Am., 88, 815–832.Google Scholar
- Kissling, E., Kradolfer, U. and Maurer, H., 1995. VELEST User's Guide—Short Introduction, Institute of Geophysics and Swiss Seismological Service, ETH, Zürich.Google Scholar
- Lienert, B.R.E. and Havskov, J., 1995. A computer program for locating earthquakes both locally and globally, Seism. Res. Lett., 66, 26–36.Google Scholar
- Müller, B., Zoback, M.L., Fuchs, K., Mastin, L., Gregersen, G., Pavoni, N., Stephansson, O. and Ljungren, C., 1992. Regional patterns of tectonic stress in Europe. J. Geophys. Res., 97, 1178–11803.Google Scholar
- Rabbel, W., Beilecke, T., Bohlen, T., Fischer, D., Frank, A., Hasenclever, J., Borm, G., Kuck, J., Bram, K., Druivenga, G., Lüschen, E., Gebrande, H., Pujol, J. and Smithson, S., 2004. Superdeep vertical seismic profiling at the KTB deep drill hole (Germany): Seismic close-up view of a major thrust zone down to 8.5 km depth. J. Geophys. Res., 109, B09309, doi:10.1029/2004JB002975.Google Scholar
- Scherbaum, F. and Johnson, J., 1992. PITSA, Programmable Interactive Toolbox for Seismological Analysis, IASPEI Software Library, Vol. 5.Google Scholar
- Sibson, R.H., 1982. Fault zone models, heat flow, and the depth distribution of earthquakes in the continental crust of the United States, Bull. Seism. Soc. Am., 72, 151–163.Google Scholar
- Snoke, J.A., Munsey, J.W., Teague A.G. and Bollinger G.A., 1984. A program for focal mechanism determination by combined use of polarity and SV-P amplitude ratio data, Earthquake Notes, 55, 15.Google Scholar
- Sonnleitner, M., 1993. Vergleich unterschiedlicher Methoden der Spannungsinversion von Erdbebendaten – am Beispiel von Erdbeben aus der Region Vogtland/westl. Böhmen. Diploma thesis, Munich University, 101 p.Google Scholar
- Stettner, G. (1971). Die Beziehungen der kohlensäureführenden Mineralwässer Nordostbayerns und der Nachbargebiete zum rhegmatischen Störungssystem des Grundgebirges. Geologica Bavarica 64, 385–394.Google Scholar
- Waldhauser, F., 2001. HypoDD – A program to compute double-difference hypocenter locations, U.S. Geological Survey Open-File Report 01–113.Google Scholar