HR: 09:45h
AN: G21D-08 [Abstracts]
TI: Nucleation of afterslip following the 2003 Tokachi-oki earthquake
AU: * Fukuda, J
EM: jfukuda@indiana.edu
AF: Indiana University, 1001 E. 10th St., Bloomington, IN 47405-1405, United States
AU: Johnson, K M
EM: kajjohns@indiana.edu
AF: Indiana University, 1001 E. 10th St., Bloomington, IN 47405-1405, United States
AU: Larson, K M
EM: kristinem.larson@gmail.com
AF: Department of Aerospace Engineering Sciences, University of Colorado, UCB 429,
Boulder, CO 80309-0429, United States
AU: Miyazaki, S
EM: miyazaki@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo, 113-
0032, Japan
AB:
We model early postseismic deformation of the 2003 Tokachi-oki
earthquake using high-rate GPS posititions calculated every twelve
minutes for the first 36 hours following the main shock.
The data show little or no motion at GPS sites immediately
after the earthquake with sudden acceleration at about 1.5 hours after
the mainshock followed by gradual deceleration.
The sudden acceleration is nearly coincident in time with the largest
aftershock (M = 7.1).
We interpret the GPS signal
during this first 36 hours as a response to afterslip on the subduction
interface. The coincidence of the largest aftershock and the onset of
afterslip may indicate that afterslip and aftershocks are governed by
the same physical process. We model the time series of
the postseismic deformation using
a spring-slider model that is assumed to obey
a rate- and state-dependent friction law.
A nonlinear inversion scheme is devised to estimate rate-state friction
parameters with the spring-slider model and the GPS time series.
We find that the 1.5 hour delay in afterslip places tight constraints
on the critical slip distance, L, which we estimate to be
on the order of 10-4 m.
This value is at the very upper end of laboratory measurements
of L which are of order 10-6 to 10-4 m.
The estimated value of a-b, an indicator of frictional stability,
is on the order of 10-3, consistent with other estimates
using postseismic data and rate-dependent friction laws.
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 1243 Space geodetic surveys
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 8118 Dynamics and mechanics of faulting (8004)
DE: 8163 Rheology and friction of fault zones (8034)
SC: Geodesy [G]
MN: 2007 Fall Meeting