Shallow crustal discontinuities inferred from waveforms of microearthquakes: Method and application to KTB Drill Site and West Bohemia Swarm Area

0457242 - GFÚ 2017 RIV US eng J - Journal Article
Hrubcová, Pavla - Vavryčuk, Václav - Boušková, Alena - Bohnhoff, M.
Shallow crustal discontinuities inferred from waveforms of microearthquakes: Method and application to KTB Drill Site and West Bohemia Swarm Area.
Journal of Geophysical Research-Solid Earth. Roč. 121, č. 2 (2016), s. 881-902. ISSN 2169-9313. E-ISSN 2169-9356
R&D Projects: GA ČR GA13-08971S; GA MŠMT LM2010008; GA ČR(CZ) GAP210/12/1491; GA ČR(CZ) GC16-19751J
Institutional support: RVO:67985530
Keywords : crustal structure * waveform stacking * microearthquakes
Subject RIV: DC - Siesmology, Volcanology, Earth Structure
Impact factor: 3.350, year: 2016

The waveforms of microearthquakes are of high frequency and complicated. They contain many phases secondarily generated at crustal interfaces and at small-scale inhomogeneities. They are highly sensitive to focal mechanisms and thus very different for each station of local networks. However, with a large number of microearthquakes, the scattered waves present in the waveforms can serve for identifying the prominent crustal discontinuities and for determining their depth. In this paper, we develop a new approach for extracting information on crustal structure from such waveforms and apply it for determining depth and lateral variations of crustal discontinuities. We show that strong dependence of microseismic waveforms on radiation pattern requires good station coverage and knowledge of focal mechanisms of the microearthquakes. Analysis of real observations is supported by waveform modeling and by analysis of radiation patterns of scattered waves. The robustness of the inversion for depth of crustal interfaces is achieved by stacking of a large number of waveforms and by applying a grid search algorithm. The method is demonstrated on two microseismic data sets of different origin: microseismicity induced during the Continental Super-Deep Drilling Project (KTB) 2000 fluid injection experiment and natural seismicity in the West Bohemia swarm region.
Permanent Link: http://hdl.handle.net/11104/0257671