Graindorge David, Spence G., Charvis Philippe, Collot Jean-Yves, Hyndman R., Tréhu A.M. (2003). Crustal structure beneath the Strait of Juan de Fuca and southern Vancouver Island from seismic and gravity analyses. Journal of Geophysical Research, 108 (B10), p. 1-23. ISSN 0418-0227.
Titre du document
Crustal structure beneath the Strait of Juan de Fuca and southern Vancouver Island from seismic and gravity analyses
Journal of Geophysical Research, 2003,
108 (B10), p. 1-23 ISSN 0418-0227
Wide angle and vertical incidence seismic data from Seismic Hazards Investigations in Puget Sound (SHIPS), gravity modeling, and seismicity are used to derive two dimensional crustal models beneath the Strait of Juan de Fuca. The Eocene volcanic Crescent Siletz terrane is significantly thicker than previously recognized and extends from near the surface to depths of 22 km or greater. For the northern strait, a weak midcrustal reflector, dipping east from 12 to 22 km depth, is inferred from wide angle reflections. A stronger deeper reflector, dipping eastward from 23 to 36 km depth, is associated with the top of "reflector band E," a zone of high reflectivity on coincident Multichannel Seismic (MCS) data, interpreted as a shear zone. A high velocity zone (7.60 ± 0.2 km s 1) between these reflectors is interpreted as a localized slice of mantle accreted with the overlying Crescent Siletz terrane. For the southern strait, no deep high velocity layer is observed and the E band reflectivity is weaker than to the north. A strong deep reflector, interpreted as the oceanic Moho dips eastward from 35 to 42 km. Seismicity within the subducting slab occurs mainly above the inferred oceanic Moho. Gravity modeling, constrained by the wide angle seismic models and seismicity, is consistent with the inferred large thickness of Crescent Siletz and high density rocks (3030 kg m 3) in the lower crust.
