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TitleStudy on the largest hydraulic-fracturing-induced earthquake in Canada: observations and static stress-drop estimation
AuthorWang, B; Harrington, R M; Liu, Y; Kao, HORCID logo; Yu, HORCID logo
SourceBulletin of the Seismological Society of America 2020 p. 1-12,
Alt SeriesNatural Resources Canada, Contribution Series 20200033
PublisherSeismological Society of America
Mediapaper; on-line; digital
File formatpdf
ProvinceBritish Columbia
NTS94A; 94H; 93O/09; 93O/10; 93O/11; 93O/14; 93O/15; 93O/16; 93P/09; 93P/10; 93P/11; 93P/12; 93P/13; 93P/14; 93P/15; 93P/16; 94B/01; 94B/02; 94B/03; 94B/06; 94B/07; 94B/08; 94B/09; 94B/10; 94B/11; 94B/14; 94B/15; 94B/16; 94G/01; 94G/02; 94G/03; 94G/06; 94G/07; 94G/08; 94G/09; 94G/10; 94G/11; 94G/14; 94G/15; 94G/16
AreaFort St. John
Lat/Long WENS-123.5000 -120.0000 58.0000 55.5000
SubjectsScience and Technology; tectonics; earthquakes; fracturing; fault zones; faults; tectonic environments; seismic risk; seismic zones; seismology; hydraulic fracturing; stress analyses; Risk management
Illustrationslocation maps; histograms; spectra; plots
ProgramEnvironmental Geoscience Shale Gas - induced seismicity
Released2020 07 21
AbstractOn 17 August 2015, an Mw 4.6 earthquake occurred northwest of Fort St. John, British Columbia, possibly induced by hydraulic fracturing (HF). We use data from 8 broadband seismometers located ~50 km from the hypocenter to detect and estimate source parameters of more than 300 events proximal to the mainshock. Stress drop values estimated using seismic moment and corner frequency from single event spectra and spectral ratios range from ~1 to 35 MPa, within the typical range of tectonic earthquakes. We observe a ~5-day delay between the onset of fluid injection and the mainshock, a b-value of 0.78 for the sequence, and a maximum earthquake magnitude larger than the prediction based on the total injection volume, suggesting the Mw 4.6 sequence occurred on a pre-existing fault and that the maximum magnitude is likely controlled by tectonic conditions. Results presented here show that pre-existing fault structures should be taken into consideration, in order to better estimate seismic hazard associated with HF operations and develop schemes for risk mitigation in close proximity of HF wells.
Summary(Plain Language Summary, not published)
On 17 August 2015, an Mw 4.6 earthquake occurred northwest of Fort St. John, British Columbia, Canada. This event is considered the largest hydraulic fracturing induced earthquake in Canada. We study the seismic characteristics of this earthquake and find that the amount of stress released by its rupture is within the typical range of tectonic earthquakes. We also notice that the size of this event is disproportionally larger than that theoretically predicted from the amount of injected fluid, suggesting that it probably occurred on a pre-existing fault. We conclude that proper assessment of pre-existing faults is important in the mitigation of seismic risk from induced earthquakes.

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