| Title | A systematic study of earthquake source mechanism and regional stress field in the southern Montney unconventional play of northeast British Columbia, Canada |
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| Author | Babaie Mahani, A; Esfahani, F; Kao, H ; Gaucher, M; Hayes, M; Visser, R; Venables, S |
| Source | Seismological Research Letters vol. 91, no. 1, 2019 p. 195-206, https://doi.org/10.1785/0220190230 |
| Year | 2019 |
| Alt Series | Natural Resources Canada, Contribution Series 20190308 |
| Publisher | Seismological Society of America |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf (Adobe® Reader®); html; docx (Microsoft® Word®); jpg; csv |
| Province | British Columbia |
| NTS | 93P/09; 93P/10; 93P/11; 93P/14; 93P/15; 93P/16; 94A/01; 94A/02; 94A/03; 94A/06; 94A/07; 94A/08 |
| Area | Fort St. John; Dawson Creek |
| Lat/Long WENS | -121.3000 -120.0000 56.3500 55.6500 |
| Subjects | geophysics; environmental geology; fossil fuels; Nature and Environment; Science and Technology; Economics and Industry; petroleum resources; petroleum industry; hydrocarbon recovery; hydraulic
fracturing; seismology; earthquakes; seismicity; earthquake magnitudes; earthquake mechanisms; stress analyses; stress orientation; seismic waves; p waves; bedrock geology; structural features; faults, strike-slip; faults, reverse; grabens; pore
pressures; seismological network; Montney Formation; Kiskatinaw Seismic Monitoring and Mitigation Area; World Stress Map; Western Canada Sedimentary Basin; Fort St. John Graben; Peace River Arch |
| Illustrations | location maps; geoscientific sketch maps; focal mechanisms; seismograms; plots; rose diagrams; stereonets; graphs; tables |
| Program | Environmental Geoscience Shale Gas - induced seismicity |
| Released | 2019 12 04 |
| Abstract | We provide a close look at the source mechanism of hydraulically fractured induced earthquakes and the in situ stress field within the southern Montney unconventional play in the northeast British
Columbia, Canada. P-wave first-motion focal mechanisms were obtained for 66 earthquakes with magnitudes between 1.5 and 4.6. Results show that strike-slip movement is the prevailing source mechanism for the events in this area, although reverse
faulting is also observed for a few earthquakes. The best-fitting nodal plane mostly strikes at ~N60° E, with most events having dip angles of >60°. Using the Martinez-Garzon et al. (2014) stress inversion module, we obtained the orientation of the
three principal compressive stress (S1>S2>S3) and the relative intermediate principal stress magnitude (R) in five clusters. Assuming the best-fitting nodal plane to be the causative fault, R values are mostly between 0.8 and 0.9 suggesting that the
magnitude of S2 and S3 are similar, which is consistent with strike-slip or reverse-faulting regimes. The plunge of S1 varies between 1° and 3°, with its trend varying between N21°E and N34°E. On the other hand, the plunge of S3 varies between 22°
and 50°, with its trend varies between N68°W and N58°W. Following Lund and Townend (2007), we calculated the trend of maximum horizontal stress to vary from N22°E to N33°E, in comparison with the average trend of N41°E from the World Stress Map
(Heidbach et al., 2016). Through analysis of the Coulomb failure criterion and Mohr diagrams, we estimated the amount of pore-pressure increase necessary to initiate shear slip to range between 4 and 29 MPa (average of 14±8 MPa) in the study area.
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| Summary | (Plain Language Summary, not published)
We study the source mechanism of hydraulically-fractured induced earthquakes and the in situ stress field in northeast British Columbia. 66 earthquakes
with magnitudes between 1.5 and 4.6 were examined. Results show that strike-slip movement is the prevailing source mechanism for the events in this area, although reverse faulting is also observed for a few earthquakes. We also obtained the
orientation of the stress regimes for 5 earthquake clusters. The plunge of the maximum stress varies between 1º to 3º with its trend varies between N21ºE to N34ºE. The maximum horizontal stress varies from N22ºE to N33ºE. The coefficient of internal
friction is estimated to be 0.62. An average pore pressure increase of 14 ± 8 MPa is needed to initiate the rupture of an induced earthquake. |
| GEOSCAN ID | 315672 |
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