HR: 1330h
AN: T52A-0239    [PDF]
TI: Spatio-temporal Evolution of On-going Tokai Slow Thrust Slip Event, Central Japan
AU: * Miyazaki, S
EM: s.miyazaki@stanford.edu
AF: Earthquake Research Institute, University of Tokyo, 1-1 Yayoi-1, Bunkyo-ku, Tokyo, 113-0032 Japan
AU: * Miyazaki, S
EM: s.miyazaki@stanford.edu
AF: Stanford University, Mitchell Building, Stanford University, Stanford, CA 94305 United States
AU: Segall, P
EM: segall@stanford.edu
AF: Stanford University, Mitchell Building, Stanford University, Stanford, CA 94305 United States
AU: Kato, T
EM: teru@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute, University of Tokyo, 1-1 Yayoi-1, Bunkyo-ku, Tokyo, 113-0032 Japan
AU: McGuire, J
EM: jmcguire@whoi.edu
AF: Woods Hole Oceanographic Institution, Clark South 272A, Woods Hole, MA 02543 United States
AU: Hatanaka, Y
EM: hata@gsi.go.jp
AF: Geographical Survey Institute, Kitasato-1, Tsukuba, Ibaraki, 305-0081 Japan
AB: We investigate an on-going slow thrust slip event that occurred at a subduction zone along the Nankai Trough off central Japan. The area we investimate, referred as the Tokai seismic gap, is located to the east of the 1944 Tonankai earthquake, which did not slip in the 1944 event. Continuous GPS data from April 1996 to the end of 1999 shows that the stations in this region have secular velocities of $\sim 2 cm/yr$ to the northwest relative to the landward plate. The GPS time series show an abrupt increase in rate in late June, 2000. The accelerated rate is currently on-going. We model this non-secular deformation, which we refer to the 2000 Tokai slow slip event, by transient slip at the plate interface and estimate their distribution with Kalman Filter based inversion methods. This event initiated around $(137.3^{\circ}E, 34.9^{\circ}N)$ almost at the same time of the onset of volcanic activity on Miyake-jima in late June, 2000. This suggests that the 2000 Tokai slow slip event is triggered by the volcanic activity on Miyake-jima. Then the locus of the slip propagated to $(137.5^{\circ}E, 34.75^{\circ}N)$ in second half of 2000, and kept slipping at the maximum rate of $\sim 15cm/yr$ through 2001. The peak slip-rate propagated to around $(137.75^{\circ}E, 34.9^{\circ}N)$ in early 2002. The depth of slip zone is $\sim 25km$, which may correspond to the lower edge of the seismogenic zone for the anticipated Tokai earthquake defined from seismicity. The cumulative moment magnitude of the slow slip event to date is $M_W \sim 6.8$. The duration of this event is longer than previously studied slow slip events using GPS data, including the 1996 Bungo slow slip event (about 1 year) and the 1996 and the 2000 Boso slow events (a few weeks).
DE: 1206 Crustal movements--interplate (8155)
DE: 1243 Space geodetic surveys
DE: 8150 Plate boundary--general (3040)
DE: 8164 Stresses--crust and lithosphere
SC: Tectonophysics [T]
MN: 2003 Fall Meeting