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Crack-tip Stress Field, Coulomb Failure, and the Spectral Characteristics of Tensile Rupture
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 74th EAGE Conference and Exhibition incorporating EUROPEC 2012, Jun 2012, cp-293-00091
- ISBN: 978-90-73834-27-9
Abstract
A simple geodynamical framework has been developed for simulation of frac-induced microseismicity. Subject to exceedance of a threshold value of time-dependent Coulomb failure stress, microseismicity is postulated to occur at random locations and with event magnitudes that satisfy the Gutenberg-Richter magnitude-recurrence relation. Simulations using this approach have many characteristics of observed microseismic clouds. Walter-Brune source spectra are considered for both tensile and shear events, which are parameterized by P- and S-wave corner frequencies and DC displacement factors. Pure tensile events may be distinguished from shear slip events based on low S/P amplitude ratios. Finally, a crack that opens and closes very quickly is characterized by periodic resonance and spectral notches similar to observed spectra of some low-frequency events.