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TitleEvidence for both crustal and mantle earthquakes in the subducting Juan de Fuca plate
AuthorCassidy, J FORCID logo; Waldhauser, F
SourceGeophysical Research Letters vol. 30, no. 2, 1095, 2003 p. 67 1-67 4, Open Access logo Open Access
LinksAbstract - Résumé
Alt SeriesGeological Survey of Canada, Contribution Series 2002062
Mediapaper; on-line; digital
File formatpdf
ProvinceBritish Columbia
NTS92B; 92C
Lat/Long WENS-126.0000 -121.0000 50.0000 47.0000
Subjectsgeophysics; structural geology; tectonics; subduction; subduction zones; plate tectonics; velocity surveys; seismic data; earthquakes; seismicity; oceanic crust; downgoing slab; earthquake mechanisms
Illustrationsgeological sketch maps; graphs
Released2003 01 31
AbstractWe investigate the relationship between high-precision hypocentres in the subducting Juan de Fuca plate beneath southwest British Columbia, and the velocity structure from receiver function analysis and reflection seismic data. 108 earthquakes at depths of 40 to 65 km were relocated using a double-difference algorithm to obtain precise earthquake locations. Correlation of the relocated seismicity with structural information shows a concentration of earthquakes near the top of the subducting oceanic crust, and a deeper layer of seismicity in the uppermost mantle of the subducting Juan de Fuca plate. The strong correlation of the seismicity with the structure of the subducting plate suggests that seismic failure is caused by changes in mechanical strength within the plate, supporting the hypotheses that phase transformations and thermal-petrological conditions play an important role in the seismogenesis of double-seismic zones.

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