| Title | Geometry of the subducting Juan de Fuca plate: new constraints from SHIPS98 |
| Download | Download (whole publication) |
| Author | Tréhu, A M; Brocher, T M; Creager, K C; Fisher, M A; Preston, L A; Spence, G; SHIPS98 Working Group |
| Source | The 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. 25-32, https://doi.org/10.4095/222491 (Open Access) |
| Links | Online - En ligne
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| Year | 2002 |
| Alt Series | United States Geological Survey, Open-file Report 02-328 |
| Publisher | Natural Resources Canada |
| Meeting | Intraslab Earthquakes in the Cascadia Subduction System: Science and Hazards; Victoria; CA; September 18-21, 2000 |
| Document | open file |
| Lang. | English |
| Media | on-line; digital |
| Related | This 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 format | pdf |
| Province | Western offshore region |
| NTS | 92A; 92B |
| Area | Georgia Strait; Puget Sound; Juan de Fuca Sound; Olympic Mountains; Olympic Peninsula; United States; Canada |
| Lat/Long WENS | -126.0000 -122.0000 49.0000 47.0000 |
| Subjects | tectonics; structural geology; geophysics; subduction zones; plate tectonics; tectonic elements; tectonic environments; tectonic interpretations; plate motions; subduction; lithosphere; oceanic
lithosphere; deformation; seismicity; seismic surveys; seismic surveys, ship; seismic reflection surveys; seismic velocities; Cascadia Subduction Zone; Cascadia Margin; Juan de Fuca Plate; Juan de Fuca Slab; Mendocino Transform; SHIPS98; geological
hazards; intraslab earthquakes; convergence; Cenozoic |
| Illustrations | sketch maps; seismic profiles; velocity models; graphs |
| Released | 2002 06 11; 2016 08 31 |
| Abstract | We have processed seismic reflection profiles acquired in the Strait of Juan de Fuca, inverted travel times of first arrivals from onshore recordings of the offshore shots to determine the velocity of
the upper crust in this region and inverted the travel times of first and secondary arrivals that undershoot the central core of the Olympic Mountains. The seismic reflection profiles show a pattern of crustal reflectivity similar to that recorded
beneath Vancouver Island. Inversion of first arrivals, interpreted to be diving waves through the upper and mid-crust indicate a 5 - 7 km-deep linear, northwest-trending basin beneath the southwestern shore of the Strait and uplift of the basement
Crescent terrane rocks beneath the northwestern shore. Velocities beneath the central Olympic Peninsula at 15 - 25 km depth show strong lateral variation, with higher velocities underlying the surface exposures of the Crescent terrane and lower
velocities at these depths beneath the Olympic core rocks. Inversion of secondary seismic arrivals interpreted to be reflections from the base of the crust of the subducted Juan de Fuca plate indicate that the Moho is at a depth of about 34 km
beneath the western Strait of Juan de Fuca and dips about 7o to the east, reaching a depth of about 46 km beneath the eastern boundary of Olympic National Park. Correlating these results with results of previous experiments on Vancouver Island and in
southwestern Washington confirm earlier interpretations of an arch in the subducted slab beneath the Olympic peninsula but indicate that the arch is asymmetric and less pronounced than previously thought. We attribute both the northwest-trending
folding of the Crescent terrane and the asymmetry in the shape of the subducting slab to resistance to the northward motion of the Paleocene-age Cascadia forearc terrane by the thick lithosphere of the pre-Tertiary terranes of British
Columbia. |
| GEOSCAN ID | 222491 |
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