Usage
  • 50 views
  • 181 downloads

Source Analysis of Induced Earthquakes in the Western Canada Sedimentary Basin

  • Author / Creator
    Wang,Ruijia
  • It has been long known that industrial activities can trigger earthquakes and the topic of “induced earthquake” embraces a great deal of scientific interest in recent years. Globally, several damaging events (i.e., Mw>5) have been linked with fluid injection/extraction. In the Western Canada Sedimentary Basin (WCSB) alone, hundreds of events have been associated with local hydraulic fracturing (HF) operations for shale gas exploration. In this thesis, I present my recent work that systematically analyzed two ML>4 HF induced earthquakes and explore the source characteristics of recent induced/natural earthquakes within the WCSB. The first record-breaking (i.e., “red-light” earthquake with ML>4) earthquake (ML=4.4, Mw=3.9) occurred on June 13, 2015 in western-central Alberta, Canada. Employing the moment tensor inversion metrics, I revealed the strike-slip mechanism of this earthquake and further improved the accuracy of its hypocentral location. Our spatial grid search, based on moment tensor inversion, confirmed the association between this event and nearby HF operations within the Duvernay play at a depth of around 3.5 km, coinciding with the hypocentral depth of this earthquake. The largest earthquake (i.e., the second “red-light” earthquake) in Alberta in the past decade shook the town of Fox Creek, on January 12, 2016. Similar to other Mw~3 earthquakes, the ML=4.8 event exhibits a dominant strike-slip (strike=184°) mechanism with limited non-double-couple (non-DC) components (~22%). Furthermore, industry-contributed local seismic recordings permit high-precision detection analysis and unveil 1108 smaller events within 3 km radius of the iii epicenter of the main event. The detected cluster shows close spatial-temporal relation to a nearby HF well and prefers high-angle N-S trending faults, which mirrorss the Pine Creek fault zone reported by earlier studies of active source seismic and aeromagnetic data. In chapter 5, I systematically compared 33 well-resolved focal mechanisms in the WCSB. Most of the regional seismicity is dominated by strike-slip/thrust faulting regimes, whereas limited (but consistent) non-DC components are obtained from injection-induced seismicity in central Alberta. I interpret the persistent compensated-linear-victor-dipole (CLVD) components (Mw2.1-3.8) as reflecting fracture growth and/or non-coplanar faults slippages during HF stimulations. I further expand the moment tensor decomposition analysis to four representative classes of induced seismicity globally and find that the overall contribution of non-DC components is largely comparable between induced and tectonic earthquakes.

  • Subjects / Keywords
  • Graduation date
    Fall 2018
  • Type of Item
    Thesis
  • Degree
    Doctor of Philosophy
  • DOI
    https://doi.org/10.7939/R3Z60CJ0B
  • License
    Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.