|2009 Portland GSA Annual Meeting (18-21 October 2009)|
|Paper No. 273-2|
|Presentation Time: 1:50 PM-2:05 PM|
DEFORMATION OF THE CASCADIA ACCRETIONARY PRISM DRIVEN BY MEGATHRUST EARTHQUAKES
WANG, Kelin, Geological Survey of Canada, Pacific Geoscience Centre, 9860 West Saanich Road, Sidney, BC V8L 4B2, Canada, email@example.com and HU, Yan, School of Earth and Ocean Sciences, University of Victoria, Victoria, BC V8W 2Y2, Canada|
An accretionary prism typically consists of an outer wedge and an inner wedge, with the former featuring much more active deformation and a steeper surface slope. According to the dynamic Coulomb wedge theory, the inner wedge overlies the megathrust seismogenic zone which experiences stress drop during interplate earthquakes, but the outer wedges overlies the shallower aseismic (rate-strengthening) part of the megathrust which experiences stress increase during earthquakes. During most of the interseismic period when the seismogenic zone is locked, the shallow zone tends to relax, such that the outer wedge is in a stable state. It is the stress increase during earthquakes that drives the outer wedge into a state of compressive failure. Therefore, permanent deformation of the outer wedge takes place episodically during and shortly after great earthquakes. The structural transition between the inner and outer wedges may or may not be well defined, but the stress transition is always gradational such that the inner wedge may also experience limited compressive deformation. The stress regime and structure are also affected by other processes such as basal erosion and underplating.
The dynamic Coulomb wedge model readily applies to most of southern Cascadia.
2009 Portland GSA Annual Meeting (18-21 October 2009)
General Information for this Meeting
|Session No. 273|
Living on the Edge: Deformation along the Cascadia Margin
Oregon Convention Center: B110/111/112
1:30 PM-5:30 PM, Wednesday, 21 October 2009
Geological Society of America Abstracts with Programs, Vol. 41, No. 7, p. 701
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