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Spatiotemporal Variations in Crustal Seismic Anisotropy Surrounding Induced Earthquakes Near Fox Creek, Alberta
Author(s) -
Li Tianyang,
Gu Yu Jeffrey,
Wang Zizhen,
Wang Ruijia,
Chen Yunfeng,
Song TehRu Alex,
Wang Ruihe
Publication year - 2019
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2018gl081766
Subject(s) - geology , seismology , induced seismicity , anisotropy , shear wave splitting , focal mechanism , shear (geology) , seismic anisotropy , hydraulic fracturing , sedimentary rock , fault (geology) , slip (aerodynamics) , geophysics , petrology , geotechnical engineering , geochemistry , physics , quantum mechanics , mantle (geology) , thermodynamics
This study analyzes earthquake recordings from four near‐source (<10 km) stations near Fox Creek, Alberta, a region known for hydraulic fracturing‐induced seismicity. We examine the spatiotemporal variations of focal mechanisms and seismic anisotropy in the sedimentary strata. The focal mechanisms of surrounding earthquake swarms are generally consistent with the strike‐slip mechanism of the M L 4.6 earthquake, favoring a flower type of fault structure. The NE‐SW‐orientated fast splitting direction, determined from the shear wave splitting measurements, reflects the combined effects of (1) N‐S faults and (2) NE‐SW time‐dependent hydraulically stimulated fractures. The latter effect dominates the apparent anisotropy during the days leading to the mainshock, while its contributions are reduced by 60–70% after the mainshock. Loss of fluid into the fault damage zone, which causes the closure of fractures, is responsible for the observed spatiotemporal variation of seismic anisotropy near the hydraulic fracturing well.