HR: 08:00h
AN: T11F-01 INVITED    [Abstracts]
TI: The complex evolution of transient slip revealed by precise tremor locations in western Shikoku, Japan
AU: * Shelly, D R
EM: dshelly@seismo.berkeley.edu
AF: University of California, Berkeley, Dept. of Earth and Planetary Science, 307 McCone Hall #4767, Berkeley, CA 94720, United States
AU: Beroza, G C
EM: beroza@pangea.stanford.edu
AF: Stanford University, Dept. of Geophysics 397 Panama Mall, Stanford, CA 94305, United States
AU: Ide, S
EM: ide@eps.s.u-tokyo.ac.jp
AF: University of Tokyo, Dept. of Earth and Planetary Science Hongo 7-3-1, Bunkyo-ku, Tokyo, 113-0033, Japan
AB: Transient slow slip events are increasingly being recognized as important components of strain release on faults and may substantially impact the earthquake cycle. Surface-based geodetic instruments provide estimates of the overall slip distribution in larger transients but are unable to capture the detailed evolution of such slip, either in time or space. Accompanying some of these slip transients is a relatively weak, extended duration seismic signal, known as non-volcanic tremor, which has recently been shown to be generated by a sequence of shear failures occurring as part of the slip event. By precisely locating the tremor, we can track some features of slip evolution with unprecedented resolution. Here, we analyze two weeklong episodes of tremor and slow slip in western Shikoku, Japan. We find that these slip transients do not evolve in a smooth and steady fashion but contain numerous sub-events of smaller size and shorter duration. In addition to along-strike migration rates of about 10 km/day observed previously, much faster migration also occurs, usually in the slab dip direction, at rates of 25-150 km/hour over distances of up to 20 km. We observe such migration episodes in both the up-dip and down-dip directions. These episodes may be most common on certain portions of the plate boundary that generate strong tremor in intermittent bursts. The surrounding regions of the fault may slip more continuously, driving these stronger patches to repeated failures. Tremor activity has a strong tidal periodicity, possibly reflecting the modulation of slow slip velocity by tidal stresses.
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 7290 Computational seismology
DE: 8118 Dynamics and mechanics of faulting (8004)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting