HR: 0830h
AN: G21B-0261    [PDF]
TI: Spatio-temporal distribution of interplate coupling in southwest Japan deduced from inversion analysis
AU: * Ito, T
EM: take@seis.nagoya-u.ac.jp
AF: RCSV, Graduate School of Environmental Studies, Nagoya University, Furo-cho, Chigusa-ku, Nagoya, Aic 464-8602 Japan
AU: Hashimoto, M
EM: hasimoto@rcep.dpri.kyoto-u.ac.jp
AF: RCEP, DPRI, Kyoto UNIV., Gokasho, Uji, Kyo 611-0011 Japan
AB: We obtain the spatio-temporal distribution of the slip on the subduction interface of the Nankai trough over an entire earthquake cycle, using geodetic data (including leveling, triangulation and trilateration, sea level, and GPS surveys) observed during the last 100 years in southwest Japan. We develop a new inversion method that can treat the long-term crustal deformations, the coseismic earthquake displacements and the stress relaxation of the viscoelastic asthenosphere. From this analysis, we obtain a model that shows postseismic afterslip on the deeper part of the plate interface following the 1946 Nankaido earthquake. The significant afterslip is found beneath central Shikoku and totals about 0.8m. The slip deficit rate during the interseismic period is 5$\sim$6 cm/year in the N50$^\circ$W$\sim$N60$^\circ$W direction, which is consistent with the relative plate motion between the Philippine Sea and the Amurian plates. A strongly coupled region is found in the shallower portion ($<$30 km), and the slip deficit rate has a maximum at a depth of about 20 km. The interplate coupling is very weak on the plate interface deeper than 30 km. The amount of slip deficit reaches about 3.3m off Shikoku and about 2m off the Kii peninsula 50 years after the 1946 earthquake. This suggests that fault healing and full interplate coupling has occurred by this time along the Nankai trough.
DE: 8150 Plate boundary--general (3040)
SC: Geodesy [G]
MN: 2003 Fall Meeting