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TitleSpatiotemporal distribution of events during the first week of the 2012 Haida Gwaii aftershock sequence
AuthorFarahbod, A M; Kao, H
SourceBulletin of the Seismological Society of America vol. 105, no. 2B, 2015 p. 1231-1240, https://doi.org/10.1785/0120140173
Year2015
Alt SeriesEarth Sciences Sector, Contribution Series 20140237
PublisherSeismological Society of America
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf
ProvinceBritish Columbia
NTS103B; 103C; 103F; 103G
AreaHaida Gwaii
Lat/Long WENS-134.0000 -131.0000 54.0000 52.0000
Lat/Long WENS-134.0000 -131.0000 54.0000 52.0000
Lat/Long WENS-134.0000 -131.0000 54.0000 52.0000
Subjectsgeophysics; earthquake studies; earthquakes; earthquake risk; earthquake mechanisms; seismicity; seismic risk; seismic interpretations; seismographs
Illustrationslocation maps; seismograms; models; plots
ProgramWestern Canada Geohazards Project, Public Safety Geoscience
AbstractWe systematically relocated the 2012 Haida Gwaii aftershock sequence by re-examining continuous seismic waveforms of the Canadian National Seismographic Network (CNSN). Due to sparse station density in the source area and offshore location of the majority of events, precise determination of hypocenters is extremely challenging. Constraints on the back-azimuth and incident angle of ray paths were derived from cross-correlation of 3-component waveforms and incorporated into the locating process to improve the results. We located 1228 aftershocks for the first week after the mainshock, effectively doubled the size of the CNSN routine earthquake catalog. The distribution of aftershocks tends to form two linear trends roughly parallel to the strike of the plate margin in the NW¿SE direction. The one located updip from the mainshock within the subducting Pacific plate appears to have three clusters spanning a lateral distance of ~80 km. The other trend is located immediately to the landward side of the Queen Charlotte Fault (QCF). Only a small percentage of the events occurred on the main rupture zone. The overall area of aftershock distribution is ~120 km by ~40 km. Aftershocks overlap the southern part of the estimated rupture zone of the 1949 earthquake with no activity in the seismic gap farther to the south. Therefore, it is likely that the 2012 earthquake did not release the accumulated stress on the strike slip transform fault system. In this scenario, the possibility of a major strike-slip earthquake along the southernmost part of the QCF should not be ignored.
Summary(Plain Language Summary, not published)
We systematically relocated the 2012 Haida Gwaii aftershock sequence by re-examining continuous seismic waveforms of the Canadian National Seismograph Network (CNSN). Due to sparse station density in the source area and offshore location of the majority of events, precise determination of epicenters is extremely challenging. We located 1228 aftershocks for the first week after the mainshock, effectively doubled the size of the CNSN routine earthquake catalog. The distribution of aftershocks tends to form two linear trends roughly in the NW¿SE direction. The overall area of aftershock distribution is ~120 km by ~40 km. Aftershocks overlap the southern part of the estimated rupture zone of the 1949 earthquake with no activity in the seismic gap farther to the south. Therefore, it is likely that the 2012 earthquake did not release the accumulated stress on the strike slip transform fault system. In this scenario, the possibility of a major strike-slip earthquake along the southernmost part of the QCF should not be ignored.
GEOSCAN ID295308