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Back-projection stacking of P- and S-waves to determine location and focal mechanism of microseismic events recorded by a surface array
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SYSNO ASEP 0472493 Document Type J - Journal Article R&D Document Type Journal Article Subsidiary J Článek ve WOS Title Back-projection stacking of P- and S-waves to determine location and focal mechanism of microseismic events recorded by a surface array Author(s) Vlček, J. (CZ)
Fischer, Tomáš (GFU-E) ORCID, RID
Vilhelm, J. (CZ)Source Title Geophysical Prospecting. - : Wiley - ISSN 0016-8025
Roč. 64, č. 6 (2016), s. 1428-1440Number of pages 13 s. Publication form Print - P Language eng - English Country GB - United Kingdom Keywords microseismic monitoring ; back-projection stacking ; hypocenter location ; focal mechanism inversion Subject RIV DC - Siesmology, Volcanology, Earth Structure Institutional support GFU-E - RVO:67985530 UT WOS 000386158100002 EID SCOPUS 84951744018 DOI 10.1111/1365-2478.12349 Annotation We present an automatic method of processing microseismic data acquired at the surface by a star-like array. The back-projection approach allows successive determination of the hypocenter position of each event andof its focal mechanisms. One-component vertical geophone groups and three-component accelerometers are employed to monitor both P- and S-waves. Hypocenter coordinates are determined in a grid by back-projection stacking of theshort-time-average-to-long-time-average ratio of absolute amplitudes at vertical components and polarization norm derived from horizontal components ofthe P- and S-waves, respectively.To make the location process more efficient, calculation is started with a coarse grid and zoomed to the optimum hypocenter using an oct-tree algorithm. Thefocal mechanism is then determined by stacking the vertical component seismograms corrected for the theoretical P-wave polarity of the focal mechanism. The mechanism is resolved in the coordinate space of strike, dip, and rake angles. The method is tested on 34 selected events of adataset ofhydraulic fracture monitoring of a shale gas play in North America. It was found that, by including S-waves, the vertical accuracy of locations improved by a factor of two and is equal to approximately the horizontal location error. A twofold enhancement of horizontal location accuracy is achieved if a denser array of geophone groups is used instead of the sparse array of three-component seismometers. The determined focal mechanisms are similar to those obtained by other methods applied to the same dataset. Workplace Geophysical Institute Contact Hana Krejzlíková, kniha@ig.cas.cz, Tel.: 267 103 028 Year of Publishing 2017
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