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Activation of optimally and unfavourably oriented faults in a uniform local stress field during the 2011 Prague, Oklahoma, sequence

Cochran, Elizabeth S. and Skoumal, Robert J. and McPhillips, Devin and Ross, Zachary E. and Keranen, Katie M. (2020) Activation of optimally and unfavourably oriented faults in a uniform local stress field during the 2011 Prague, Oklahoma, sequence. Geophysical Journal International, 222 (1). pp. 153-168. ISSN 0956-540X. doi:10.1093/gji/ggaa153.

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The orientations of faults activated relative to the local principal stress directions can provide insights into the role of pore pressure changes in induced earthquake sequences. Here, we examine the 2011 M 5.7 Prague earthquake sequence that was induced by nearby wastewater disposal. We estimate the local principal compressive stress direction near the rupture as inferred from shear wave splitting measurements at spatial resolutions as small as 750 m. We find that the dominant azimuth observed is parallel to previous estimates of the regional compressive stress with some secondary azimuths oriented subparallel to the strike of the major fault structures. From an extended catalogue, we map ten distinct fault segments activated during the sequence that exhibit a wide array of orientations. We assess whether the five near-vertical fault planes are optimally oriented to fail in the determined stress field. We find that only two of the fault planes, including the M   5.7 main shock fault, are optimally oriented. Both the M 4.8 foreshock and M   4.8 aftershock occur on fault planes that deviate 20–29° from the optimal orientation for slip. Our results confirm that induced event sequences can occur on faults not optimally oriented for failure in the local stress field. The results suggest elevated pore fluid pressures likely induced failure along several of the faults activated in the 2011 Prague sequence.

Item Type:Article
Related URLs:
URLURL TypeDescription
Cochran, Elizabeth S.0000-0003-2485-4484
McPhillips, Devin0000-0003-1987-9249
Ross, Zachary E.0000-0002-6343-8400
Additional Information:Published by Oxford University Press on behalf of The Royal Astronomical Society 2020. This work is written by (a) US Government employee(s) and is in the public domain in the US. Accepted 2020 March 17. Received 2020 February 19; in original form 2019 October 31. We thank Daniel Trugman for making the GrowClust codes available and providing advice on an appropriate weighting scheme for relocation of the template and detected events. We acknowledge D. Sumy and C. Neighbors for useful discussions of early SWS findings. We thank two anonymous journal reviewers and USGS reviewers N. Farghal and J. Hardebeck for constructive reviews. The Generic Mapping Tools software was used to generate several of the figures in this paper (Wessel & Smith 1991; Wessel et al. 2013). Any use of trade, firm or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Group:Seismological Laboratory
Subject Keywords:Induced seismicity, Rheology and friction of fault zones, Seismic anisotropy
Issue or Number:1
Record Number:CaltechAUTHORS:20200625-112850000
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Official Citation:Elizabeth S Cochran, Robert J Skoumal, Devin McPhillips, Zachary E Ross, Katie M Keranen, Activation of optimally and unfavourably oriented faults in a uniform local stress field during the 2011 Prague, Oklahoma, sequence, Geophysical Journal International, Volume 222, Issue 1, July 2020, Pages 153–168,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104050
Deposited By: George Porter
Deposited On:25 Jun 2020 21:29
Last Modified:16 Nov 2021 18:27

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