HR: 0800h
AN: S21A-0204 INVITED     [Abstracts]
TI: Coseismic Slip Distribution of the 1923 Kanto Earthquake, Japan
AU: * Pollitz, F F
EM: fpollitz@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd., MS 977, Menlo Park, CA 94025 United States
AU: Nyst, M
EM: mnyst@pangea.stanford.edu
AF: U.S. Geological Survey, 345 Middlefield Rd., MS 977, Menlo Park, CA 94025 United States
AU: Nishimura, T
EM: t_nisimura@gsi.go.jp
AF: Geographical Survey Institute, Geography and Crustal Dynamics Research Center, Tsukuba, 305-0811 Japan
AU: Thatcher, W
EM: thatcher@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd., MS 977, Menlo Park, CA 94025 United States
AB: The slip distribution associated with the 1923 M=7.9 Kanto, Japan earthquake is re-examined in light of new data and modeling. We utilize a combination of first order triangulation, second order triangulation, and leveling data in order to constrain the coseismic deformation. The second order triangulation data, which have not been utilized in previous studies of 1923 coseismic deformation, are associated with only slightly smaller errors than the first order triangulation data and expand the available triangulation dataset by about a factor of 10. Interpretation of this data in terms of uniform slip models in a companion study [ Nyst et al., 2005] shows that a model involving uniform coseismic slip on two distinct rupture planes explains the data very well and matches or exceeds the fit obtained by previous studies, even one which involved distributed slip. Using the geometry of the Nyst et al. [2005] 2-plane slip model, we perform inversions of the same geodetic dataset for distributed slip. Our preferred model of distributed slip on the Philippine Sea plate interface has a moment magnitude of 7.86. We find slip maxima of ~ 8 to 9 meters beneath Odawara and ~ 7 to 8 meters beneath the Miura peninsula, with a roughly 2:1 ratio of strike-slip to dip-slip motion, in agreement with a previous study [ Wald and Somerville, 1995]. However the Miura slip maximum is imaged as a more broadly-extended feature in our study, with the high-slip region continuing from the Miura peninsula to the southern Boso peninsula region. The second order triangulation data provide good evidence for ~ 3 meters right-lateral strike slip on a 35-km long splay structure occupying the volume between the upper surface of the descending Philippine Sea plate and the southern Boso peninsula.
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
DE: 7215 Earthquake source observations (1240)
SC: Seismology [S]
MN: Fall Meeting 2005