HR: 10:50h
AN: S32B-03 INVITED    [Abstracts]
TI: Deep Tremor as a Focus of Earthquake Forecasting Research
AU: * Beroza, G C
EM: beroza@geo.stanford.edu
AF: Department of Geophysics Stanford University, 397 Panama Mall, Stanford, CA 94305-2215, United States
AB: The discovery of deep tremor has opened a new window into fault-zone processes and offers new possibilities for earthquake forecasting research. Locales where deep tremor has been extensively documented to date include the Nankai Trough, Cascadia, and Central California, which are all areas with considerable seismic potential. Deep tremor is observed to accompany slow slip, such that the combined phenomena have come to be known as episodic tremor and slip (ETS). The emerging view is that deep tremor is the seismic signature of slow slip that occurs episodically on the down-dip extension of seismogenic faults. The amount of slip in these slow slip episodes is approximately equal to the amount of slip that would have been accumulated during the time since the last ETS episode. This suggests that the tremor source may outline the down-dip edge of the locked, seismogenic zone, with the down-dip transition zone locked between ETS episodes, and relaxed during them. Thus, on faults on which tremor occurs, it should be possible to map precisely the down-dip extent of the locked zone, which is often a major source of uncertainty in assessing earthquake potential. Tremor may also prove useful for time-dependent earthquake forecasting. Due to it's strategic location, and episodic nature, deep episodic transients will accelerate stress accumulation on adjacent, shallower, locked portions of faults, which should in turn increase the likelihood of a large earthquake. Thus, tremor is a potentially important forecasting tool, though it might lead to only modest probability gains. With frequent tremor episodes, and infrequent large earthquakes, it will be difficult to test this hypothesis. A more fruitful approach may be to monitor the variation of micro-earthquake activity with respect to deep tremor, and perhaps to examine historical seismic data retrospectively for seismic tremor near the time of large earthquakes. The potential promise of this newly discovered phenomenon argues for enhanced monitoring in areas where tremor is known to occur, and in places where it is likely to occur, based on our understanding of the factors that control tremor occurrence.
DE: 7215 Earthquake source observations (1240)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 7294 Seismic instruments and networks (0935, 3025)
SC: Seismology [S]
MN: 2007 Fall Meeting