CGRG Bibliography of Canadian Geomorphology
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Author : Dragert, H.; Mazzotti, S.; Hyndman, R.D.; Wang, K.; and Schmidt, M.
Date : 2003.
Title : Recent contributions of GPS observations to seismic hazard studies along the Northern Cascadia Margin.
Publication : On the Edge: Earth Science at North America’s Western Margin. Annual Meeting of the GAC, MAC and SEG. Sheraton Wall Centre, Vancouver, British Columbia. May 25 - 28, 2003.
Issue :
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Abstract
The increasing coverage of continuous and campaign GPS stations along the Cascadia Margin, together with improvements in GPS data analyses have provided not only an unprecedented research tool for the study of regional neotectonics, but also an effective methodology for improving estimates of seismic hazard. Precise GPS observations allow direct detection of elastic strain buildup which controls both spatial and temporal occurrences of large earthquakes, exactly those seismic events which pose the largest hazard but whose recurrence intervals and spatial distributions are not well defined by our short historical records. Results from recent GPS studies have led to refinements in estimates of the extent of the region of coupling on the subduction thrust interface which is important for estimating the zone of rupture for the next megathrust earthquake and its accompanying strong motions. Recent comparisons of GPS-determined geodetic strain accumulation versus seismic strain release have improved the accuracy of return-period estimates for larger, less frequent earthquakes in the Georgia Strait/ Puget Sound seismic zone. The surface coseismic displacements recorded at continuous GPS stations for the 2001 Nisqually (M=6.8) earthquake clearly demonstrated that GPS can also be used to study the hazard associated with large ruptures deep in the subducting slab. Although GPS coverage was too sparse for this particular earthquake, recent GPS network densification will allow better definition of even such a deep rupture zone and the transfer of stress to nearby faults. Finally, the recent discovery of aseismic slip on the deeper Cascadia subduction interface suggests that stress accumulation across the locked megathrust zone can occur in discrete pulses. Such slip events could evolve into a trigger mechanism for a great thrust earthquake. Consequently, the identification and monitoring of deep aseismic slip through continuous GPS observations may lead to a time-variant estimate of seismic potential of the subduction megathrust.
Bibliography of Canadian Geomorphology