HR: 17:10h
AN: NG24B-01 INVITED     [Abstracts]
TI: Can variations in precursory seismicity be used to forecast (predict) earthquakes?
AU: * Turcotte, D L
EM: turcotte@geology.ucdavis.edu
AF: Department of Geology, University of California, One Shields Ave., Davis, CA 95616 United States
AU: Rundle, J B
EM: jbrundle@ucdavis.edu
AF: Center for Computational Science and Engineering and Department of Physics, University of California, One Shields Ave., Davis, CA 95616 United States
AU: Shcherbakov, R
EM: rshcherbakov@ucdavis.edu
AF: Center for Computational Science and Engineering, University of California, One Shields Ave., Davis, CA 95616 United States
AB: There are basically two approaches to the initiation of a major earthquake rupture. The first is to consider the fault on which the earthquake will occur. A focus is on subcritical crack growth. Although rate-and-state friction predicts a precursory creep phase, there is no observational evidence for its occurrence. Also, if the fault dominates, one would expect a systematic increase in the background seismicity during the earthquake cycle. This is not observed. The second approach is to consider that the earth's crust as a thermodynamic system. The near constant background seismicity that satisfies Gutenberg-Richter scaling is a thermal noise. This background noise generates fluctuations in stress level that are responsible for the initiation of rupture on major faults. This approach explains the relatively large variations in wait times between great earthquakes. But a more important question is whether there are observational statistical patterns precursory to major ruptures. Analogies to phase changes indicate that systematic increases in fluctuation levels may be an observable precursory effect. There is also observational support for this in the success of forecasting algorithms such as M8 and pattern informatics and the observations of accelerated moment release before large earthquakes.
DE: 7223 Seismic hazard assessment and prediction
DE: 8020 Mechanics
DE: 8159 Rheology--crust and lithosphere
DE: 7209 Earthquake dynamics and mechanics
DE: 3250 Fractals and multifractals
SC: Nonlinear Geophysics [NG]
MN: 2004 AGU Fall Meeting