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TitleThe landward limit of Cascadia Great Earthquake Rupture
AuthorHyndman, R D; Wang, K; Cassidy, J; Kao, H; Mazzotti, S; Dragert, H; Henton, J; Leonard, L; Rogers, G
Source2010 Annual Seismological Society of America Meeting, Abstracts; Seismological Research Letters vol. 81, no. 2, 2010 p. 288
Alt SeriesEarth Sciences Sector, Contribution Series 20100024
Meeting2010 Annual Seismological Society of America Meeting; Portland; US; April 21-23, 2010
Mediapaper; on-line; digital
ProvinceWestern offshore region
Subjectsgeophysics; earthquakes; earthquake mechanisms; earthquake studies; Cascadia
ProgramTargeted Hazard Assessments in Western Canada, Public Safety Geoscience
LinksOnline - En ligne
AbstractThe dominant control for megathrust shaking intensity at near-coastal cities is the landward, downdip extent of rupture. It represents the source closest approach and, with along-strike length, constrains the maximum magnitude. The updip limit and wave propagation factors are also important for shaking and tsunami generation. Some downdip estimates are for past rupture, some for the locked zone, and some for downdip limits to seismic behaviour. Bases for estimating downdip rupture extent include: (1) Modeled paleoseismic coastal subsidence, and the 1700 tsunami. (2) Locked/transition zones from modelling geodetic deformation. (3) Seismic behaviour limits from downdip temperatures, change in seismic reflection character downdip, and the ETS updip limit (with some offset). The limits to coseismic rupture and the interseismic locked zone from geodetic data are not identical because of the deformation time dependence. The rates of rupture are also important, i.e., seismic rupture, slower tsunamogenic slip, and slower long-term slip detected geodetically. A related issue is the nature and relationship of postseismic and interseismic slip and viscous relaxation. Although the differences among the estimates are important, most give similar extents, i.e., the principal rupture displacement occurs offshore beneath the outer continental shelf, and the majority of events appear to rupture most of the seismogenic region, i.e., M9. Unresolved questions include: Vertical interseismic models that involve several poorly constrained parameters, the relationship between coseismic rupture distribution and interseismic locking from geodetic data and from ETS distributions, and uncertainties in the depth to the megathrust.