Source characteristics and geological implications of the January 2016 induced earthquake swarm near Crooked Lake, Alberta

作者：Wang Ruijia^*; Gu Yu Jeffrey; Schultz Ryan; Zhang Miao; Kim Ahyi

来源：Geophysical Journal International, 2017, 210(2): 979-988.

DOI：10.1093/gji/ggx204

• North America
• Earthquake dynamics
• Earthquake source observations
• Fractures
• faults
• and high strain deformation zones
• Mechanics
• theory
• and modelling
• Transform faults

On 2016 January 12, an intraplate earthquake with an initial reported local magnitude (M-L) of 4.8 shook the town of Fox Creek, Alberta. While there were no reported damages, this earthquake was widely felt by the local residents and suspected to be induced by the nearby hydraulic-fracturing (HF) operations. In this study, we determine the earthquake source parameters using moment tensor inversions, and then detect and locate the associated swarm using a waveform cross-correlation based method. The broad-band seismic recordings from regional arrays suggest a moment magnitude (M) 4.1 for this event, which is the largest in Alberta in the past decade. Similar to other recent M similar to 3 earthquakes near Fox Creek, the 2016 January 12 earthquake exhibits a dominant strike-slip (strike = 184 degrees) mechanism with limited non-double-couple components (similar to 22 per cent). This resolved focal mechanism, which is also supported by forward modelling and P-wave first motion analysis, indicates an NE-SW oriented compressional axis consistent with the maximum compressive horizontal stress orientations delineated from borehole breakouts. Further detection analysis on industry-contributed recordings unveils 1108 smaller events within 3 km radius of the epicentre of the main event, showing a close spatial-temporal relation to a nearby HF well. The majority of the detected events are located above the basement, comparable to the injection depth (3.5 km) on the Duvernay shale Formation. The spatial distribution of this earthquake cluster further suggests that (1) the source of the sequence is an N-S-striking fault system and (2) these earthquakes were induced by an HF well close to but different from the well that triggered a previous (January 2015) earthquake swarm. Reactivation of pre-existing, N-S oriented faults analogous to the Pine Creek fault zone, which was reported by earlier studies of active source seismic and aeromagnetic data, are likely responsible for the occurrence of the January 2016 earthquake swarm and other recent events in the Crooked Lake area.

• 出版日期2017-8