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TitleIntensity of induced earthquakes in northeast British Columbia, Canada
AuthorBabaie Mahani, A; Venables, S; Kao, HORCID logo; Visser, R; Gaucher, M; Dokht, R M H; Johnson, J
SourceSeismological Research Letters 2021 p. 1-10,
Alt SeriesNatural Resources Canada, Contribution Series 20210087
PublisherSeismological Society of America
Mediapaper; on-line; digital
File formatpdf; html
ProvinceBritish Columbia
NTS93O; 93P; 94A; 94B; 94G; 94H
AreaDawson Creek; Fort St. John
Lat/Long WENS-123.0000 -120.0000 58.0000 55.5000
Subjectsgeophysics; Science and Technology; Nature and Environment; Economics and Industry; Health and Safety; seismology; seismicity; seismic risk; earthquakes; earthquake risk; earthquake magnitudes; earthquake damage; epicentres; petroleum industry; petroleum resources; hydrocarbon recovery; Western Canada Sedimentary Basin; Resource development
Illustrationslocation maps; geoscientific sketch maps; histograms; profiles; tables; plots
ProgramEnvironmental Geoscience Shale Gas - induced seismicity
Released2021 05 19
AbstractThe damage potential of induced earthquakes associated with fluid injection is a major concern in hydrocarbon resource development. An important source of data for the assessment of damage is macroseismic intensity perceived by people and structures. In the Western Canada Sedimentary Basin (WCSB) where the occurrence of seismicity is mostly related to oil and gas activities, the collection of intensity data is incomplete. In this study, we present a comprehensive dataset gathered by the BC Oil and Gas Commission in the period 2016-2020. We assign intensities to individual felt reports according to the modified Mercalli intensity (MMI) scale and associate each MMI value to an earthquake. The isoseismal map of the largest earthquake in the Septimus region of northeast British Columbia is also provided using the compiled intensity dataset complemented with data from the U.S. Geological Survey and Natural Resources Canada 'Did You Feel It?' systems along with the intensities converted from ground?motion amplitudes. We consider an approximate 10 km radius around the mainshock of 30 November 2018 earthquake with moment magnitude of 4.6 to be the meizoseismal area based on maximum intensities of 4-5. We also investigate the distance decay of intensity for shallow induced earthquakes in comparison with deeper natural events with the same magnitudes. Although intensities from shallow earthquakes (depth less than or equal to 5 km) can be higher than deep events (depth greater than or equal to 10 km) at close distances (10-15 km), they tend to decrease abruptly at greater distances to become lower than deep events. The localization of large intensities from induced earthquakes within the meizoseismal area warrants special attention in future resource developments and call for systematic intensity data collection in the WCSB.
Summary(Plain Language Summary, not published)
The intensity of ground shaking associated with induced earthquakes in the Western Canada Sedimentary Basin (WCSB) is important for regional seismic hazard assessment. However, the incompleteness of induced earthquakes (especially events with small magnitude values) in NRCan's National Earthquake Database severely impact the effort to compile a comprehensive intensity database for the WCSB. In this study, we systematically examine earthquake felt reports collected by the British Columbia Oil and Gas Commission (BCOGC) over the period of 2016-2020 that are related to injection-induced earthquakes. Each of the felt reports is given an intensity value compatible with the Modified Mercalli Intensity scale used by NRCan. Our observations indicate that the intensity of events shallower than 5 km decreases much more quickly with epicentral distance than deeper events (>10 km). Thus from a seismic hazard's point of view, special attention should be given to the immediate vicinity of injection wells where the likelihood of having induced earthquakes is the highest.

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