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TitleSource Characteristics of the 2012 Haida Gwaii Earthquake Sequence
AuthorKao, H; Shan, S -J; Farahbod, A M
SourceBulletin of the Seismological Society of America vol. 105, no. 2B, 2015 p. 1206-1218, https://doi.org/10.1785/0120140165
Year2015
Alt SeriesEarth Sciences Sector, Contribution Series 20140238
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 54.0000
Lat/Long WENS-134.0000 -131.0000 54.0000 54.0000
Lat/Long WENS-134.0000 -131.0000 54.0000 54.0000
Subjectsgeophysics; earthquakes; earthquake risk; earthquake studies; earthquake mechanisms; seismicity; seismic risk; seismic interpretations
Illustrationslocation maps; plots; tables; schematic diagrams
ProgramWestern Canada Geohazards Project, Public Safety Geoscience
AbstractWe systematically relocate all the significant events in the 2012 Haida Gwaii earthquake sequence and determine their moment-tensor solutions from waveform inversion. Focal mechanism of the mainshock shows low-angle thrust faulting along a shallowly dipping plane with a strike parallel to the Queen Charlotte Fault (QCF), consistent with the inference of Pacific plate underthrusting beneath the overriding North America plate. The epicenter of the mainshock is located ~7 km landward from the surface trace of the QCF, suggesting that the nucleation of the rupture was near the bottom of the seismogenic (locked) interface. Significant aftershocks appear to distribute around the main rupture zone with most events located immediately seaward from the deformation front. The majority of these events show normal-faulting mechanisms that are probably associated with the bending stress near the deformation front as the Pacific plate subducts. Several normal and strike-slip events at deeper depths within the Pacific plate show a consistent pattern of T-axis in the downdip direction, implying that the subducted plate is under a stress regime of downdip extension. Only a few strike-slip events were observed along the QCF. The limited size and distribution of these events suggest that most of the elastic strain accumulated along the QCF was not released during the 2012 Haida Gwaii sequence. The likelihood of having major strike-slip earthquakes along the southernmost part of the QCF system in the future cannot be ignored.
Summary(Plain Language Summary, not published)
We systematically relocate all the significant events in the 2012 Haida Gwaii earthquake sequence and determine their source characteristics from waveform inversion. The mainshock shows low-angle thrust faulting mechanism along a shallowly dipping plane with a strike parallel to the Queen Charlotte Fault (QCF). This is consistent with the inference of Pacific plate underthrusting beneath the overriding North America plate. The nucleation of the rupture was near the bottom of the locked interface. Significant aftershocks appear to distribute along the perimeter of the main rupture zone. Only a few strike-slip events were observed along the QCF. The limited size and distribution of these events suggest that most of the elastic strain accumulated along the QCF was not released during the 2012 Haida Gwaii sequence. The likelihood of having major strike-slip earthquakes along the southernmost part of the QCF system in the future cannot be ignored.
GEOSCAN ID295309