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Title3D ground motion in the Georgia Basin region of SW British Columbia for intra-slab earthquake scenarios
AuthorMolnar, S; Cassidy, J FORCID logo; Dosso, S; Olsen, K
SourceEos, Transactions of the American Geophysical Union vol. 90, no. 22, 2009, 1 pages
Alt SeriesEarth Sciences Sector, Contribution Series 20080721
MeetingAmerican Geophysical Union 2009 Joint Assembly; Toronto; CA; May 24-27, 2009
Mediapaper; on-line; digital
ProvinceBritish Columbia
Subjectsgeophysics; engineering geology; earthquakes; earthquake studies; earthquake mechanisms; strong motion seismology; plate motions; seismicity; s waves; seismic waves; surface wave studies; Georgia Basin
ProgramReducing Risk from Natural Hazards
AbstractWe investigate long-period (> 2 s) ground motions in the Georgia basin region of SW British Columbia (BC) for intra-slab earthquake scenarios using 3D finite-difference simulations of viscoelastic wave propagation. The Georgia basin is a site of concentrated deep (25-80 km) Juan de Fuca plate seismicity in a region with over 2 million inhabitants and vital economic facilities. Earthquake waves are altered by 3D basin structure due to the generation of surface waves and S-wave focusing at the basin edges. To validate our simulation, synthetic surface waveforms are compared with 32 strong- and weak-motion recordings of the 2001 Mw 6.8 Nisqually earthquake spanning from Puget Sound, Washington, to southern BC. To investigate intra-slab earthquake scenarios we initiate the Nisqually-model source in six different locations beneath the NW-SE trending Georgia basin. The largest ground motions always occur NW of the source location, so the peak ground velocity pattern alters dramatically with source location. In all cases, ground motion is amplified at the edges of the basin due to S-wave focusing, as well as along a NE-SW velocity contrast that runs beneath the city of Vancouver. In greater Vancouver, the largest simulated ground motions (100 cm/s) occur for sources located beneath the SE portion of the basin.

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