caa a22 4500 475813200 CHVBK 20180406123803.0 cr unu---uuuuu 170329e20000901xx s 000 0 eng 10.1007/PL00001121 doi (NATIONALLICENCE)springer-10.1007/PL00001121 Upper Crustal Velocity Structure of the Southwestern Canadian Cordillera from Explosion Recordings on the WCTN Earthquake Seismic Net [Elektronische Daten] [S. J. Fallows, G. D. Spence, G. C. Rogers] —The digital seismic network used to monitor earthquakes in southwestern British Columbia recorded explosions from Lithoprobe's Southern Cordillera Refraction Experiment (SCoRE) in 1989 and 1990 and from the USGS Pacific Northwest Refraction Survey in 1991. Both P and S waves were recorded. The geographical distribution of the shots and receiver stations enabled a large three-dimensional area to be sampled. For ray paths considered to be in the top 10 km of the crust, we used a tomographic inversion procedure to estimate the 2-D distribution of upper crustal P- and S-wave velocities within blocks of a refracting velocity grid, located beneath a near surface velocity layer of uniform thickness. The P-wave velocity distribution mapped the subsurface location of several terranes in the southwest Cordillera. Volcanic rocks of Wrangellia terrane, which is the principal component of the Insular Belt, were characterized by upper crustal velocities > 6.3 km s −1, whereas plutonic rocks of the Coast Belt had velocities < 6.3 km s−1. East of southern Vancouver Island, the velocity distribution indicated that Wrangellia extends in the subsurface beneath the Coast Belt for about 130 km eastward of the surface location of the Insular/Coast Belt boundary. A portion of the southern boundary of Wrangellia was also delineated by the P-velocity map, which suggested that metamorphic rocks of the Northwest Cascades Thrust System may extend beneath sedimentary cover as far west as south-central Georgia Strait. Inverted S-wave velocities were typically 3.6-3.7 km s−1. Corresponding values of Poisson's ratio were 0.27-0.28 over Vancouver Island and 0.20-0.24 in the Coast Belt. The higher values for Vancouver Island likely reflect the high mafic content of Wrangellia volcanics, compared to the high quartz content of the Coast Belt plutonics. Birkhäuser Verlag Basel,, 2000 Key Words: Seismic refraction, crustal velocity, Canadian Cordillera, tomographic inversion, earthquake seismic net, shear-wave velocities nationallicence Fallows S. J. School of Earth and Ocean Sciences, University of Victoria, Victoria, B.C. V8W 2Y2, Canada., CA aut Spence G. D. School of Earth and Ocean Sciences, University of Victoria, Victoria, B.C. V8W 2Y2, Canada., CA aut Rogers G. C. Geological Survey of Canada, Pacific Geoscience Centre, P.O. Box 6000, Sidney, B.C. V8L 4B2, Canada., CA aut https://doi.org/10.1007/PL00001121 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/PL00001121 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Fallows S. J. School of Earth and Ocean Sciences, University of Victoria, Victoria, B.C. V8W 2Y2, Canada., CA aut NATIONALLICENCE 700 1- Spence G. D. School of Earth and Ocean Sciences, University of Victoria, Victoria, B.C. V8W 2Y2, Canada., CA aut NATIONALLICENCE 700 1- Rogers G. C. Geological Survey of Canada, Pacific Geoscience Centre, P.O. Box 6000, Sidney, B.C. V8L 4B2, Canada., CA aut Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer