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TitlePrecise relocations of slab seismicity in the northern Cascadia subduction zone
DownloadDownload (whole publication)
AuthorCassidy, J F; Waldhauser, F
SourceThe Cascadia subduction zone and related subduction systems - seismic structure, intraslab earthquakes and processes, and earthquake hazards; by Kirby, S (ed.); Wang, K (ed.); Dunlop, S (ed.); Geological Survey of Canada, Open File 4350, 2002 p. 69-74, (Open Access)
LinksOnline - En ligne
Alt SeriesUnited States Geological Survey, Open-file Report 02-328
PublisherNatural Resources Canada
MeetingIntraslab Earthquakes in the Cascadia Subduction System: Science and Hazards; Victoria; CA; September 18-21, 2000
Documentopen file
Mediaon-line; digital
RelatedThis publication is contained in Kirby, S; Wang, K; Dunlop, S; (2002). The Cascadia subduction zone and related subduction systems - seismic structure, intraslab earthquakes and processes, and earthquake hazards, Geological Survey of Canada, Open File 4350
File formatpdf
ProvinceWestern offshore region
NTS92A; 92B
AreaGeorgia Strait; Puget Sound; Juan de Fuca Sound; United States of America; Canada
Lat/Long WENS-126.0000 -122.0000 49.0000 47.0000
Subjectstectonics; geophysics; subduction zones; plate tectonics; tectonic elements; tectonic environments; tectonic interpretations; plate motions; subduction; lithosphere; oceanic lithosphere; earthquake mechanisms; earthquake studies; earthquake risk; earthquakes; seismicity; seismographs; Cascadia Subduction Zone; Juan de Fuca Plate; Cascadia Forearc; geological hazards; intraslab earthquakes
Illustrationssketch maps; graphs
Released2002 06 11; 2016 08 31
AbstractThe Gulf Islands region of southwest British Columbia is an ideal location to study, in detail, slab seismicity of the subducting Juan de Fuca plate. Here, there is abundant slab seismicity, a relatively dense network of seismograph stations to obtain accurate hypocenters and some recently deployed three-component broadband stations to constrain the velocity structure. We have relocated slab seismicity
near 50 - 60 km depth in the Gulf Island region using a "double difference" earthquake relocation algorithm designed to provide high-resolution relative hypocenter locations over large distances. The precise relative locations obtained for an initial test set of 27 deep earthquakes in a narrow corridor near Saturna Island, B.C., indicates that most of the slab seismicity here is in a three to four kilometer-thick region dipping at 20° to the northeast. There is some suggestion of a deeper parallel band of seismicity (7 - 9 km) below the top of the upper band that may be located in the upper mantle of the Juan de Fuca plate.