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TitleThermal condition of the 27 October 2012 Mw 7.8 Haida Gwaii subduction earthquake at the obliquely convergent Queen Charlotte Margin
AuthorWang, K; He, J; Schulzeck, F; Hyndman, R D; Riedel, M
SourceBulletin of the Seismological Society of America vol. 105, no. 2B, 2015 p. 1-11, https://doi.org/10.1785/0120140183
Year2015
Alt SeriesEarth Sciences Sector, Contribution Series 20140106
PublisherSeismological Society of America
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf
ProvinceBritish Columbia
NTS103B; 103C
AreaHaida Gwaii; Queen Charlotte Island
Lat/Long WENS-132.0000 -130.7500 52.7500 52.0000
Subjectsgeophysics; earthquakes; earthquake magnitudes; earthquake mechanisms; thermal analyses; subduction; crustal movements
Illustrationslocation maps; block diagrams; plots; cross-sections
ProgramWestern Canada Geohazards Project, Public Safety Geoscience
AbstractThe 2012 Mw 7.8 Haida Gwaii earthquake confirmed very oblique subduction and slip partitioning at the southern Queen Charlotte margin. In this study, we re-examine the thermal regime near the earthquake using new model constraints and with the recognition that hydrothermal circulation in the subducting oceanic crust can significantly affect the margin thermal regime. The observed heat flow values are extremely high just seaward of the trench but decrease rapidly landward. We explain this pattern as the consequence of very vigorous hydrothermal circulation in the subducting oceanic crust. Using a finite-element model, we simulate the thermal effect of the circulation using a high-conductivity proxy that represents a very high Nusselt number in an aquifer along the top of the oceanic plate. Our thermal model indicates that the temperature at the intersection of the megathrust and the strike-slip Queen Charlotte fault (QCF) just seaward of the coast is about 350° C, approximately the limit of seismogenic behavior, and cooler than previous models that did not include hydrothermal circulation. The change of plate motion kinematics across the QCF approximately coincides with a down-dip transition of the thermally controlled seismogenic behavior of the megathrust. Seaward of the QCF, the shallow megathrust accommodates mainly the margin-normal component of relative plate motion, with the strike-slip component accommodated by the QCF. This portion of the megathrust exhibits stick slip and produced the 2012 Haida Gwaii earthquake. Landward of the QCF, the megathrust fully accommodates the very oblique motion of the oceanic plate beneath the continental crust and exhibits creep.
Summary(Plain Language Summary, not published)
The 2012 M 7.7 Haida Gwaii earthquake verified the presence of seismic and tsunami hazard from megathrust earthquakes at the southern Queen Charlotte margin. We study the geothermal regime near the earthquake. Our results indicate that the temperature at the intersection of the megathrust and the strike-slip Queen Charlotte Fault (QCF) just seaward of the coast is about 350C, approximately the upper thermal limit of seismogenic behavior. Seaward of the QCF, the shallow megathrust accommodates the margin-normal component of relative plate motion and exhibits "stick-slip" that is responsible for large earthquakes. Landward of the QCF, the megathrust fully accommodates the very oblique plate motion and exhibits creep that inhibits large earthquakes.
GEOSCAN ID294814