HR: 12:05h
AN: NG32A-06    [Abstracts]
TI: Active Seismic Monitoring for Earthquake Forecasting
AU: Artamonova, M
EM: marina_art@sbcglobal.net
AF: SVR Electronics, 1148 Nogales st., Lafayette, CA 94549 United States
AU: * Korneev, V
EM: vakorneev@lbl.gov
AF: LBNL, 1 Cyclotron Rd, Berkeley, CA 94720 United States
AB: Earthquake prediction remains high priority issue for disaster prevention. Study of the M6.0 2004 Parkfield and M7.0 1989 Loma Prieta strike-slip earthquakes on the San Andreas Fault (SAF) reveal seismicity peaks in the surrounding crust several months prior to the main events. Earthquakes directly within the SAF zone were intentionally excluded from the analysis because they manifest stress-release processes rather than stress accumulation. The observed increase in seismicity is interpreted as a signature of the increasing stress level in the surrounding crust, while the peak that occurs several months prior to the main event and the subsequent decrease in seismicity are attributed to damage-induced softening processes. Furthermore, in both cases there is a distinctive zone of low seismic activity that surrounds the epicentral region in the pre-event period. The increase of seismicity in the crust surrounding a potential future event and the development of a low-seismicity epicentral zone can be regarded as promising precursory information that could help signal the arrival of large earthquakes. We modeled the seismicity precursor phenomena using finite-element 2D model capable to replicate non-linear breaking of elastic rock. The distinctive seismicity peak was observed for a model simulating SAF properties at Park field. Such peaks are likely to be a good mid-term precursors allowing to declare alerts several months before earthquakes and pointing on their epicenter regions. The short tern alerts require use of active sources and their proper placement in order to monitor the developments of rock softening processes.
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 4425 Critical phenomena
DE: 7209 Earthquake dynamics (1242)
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 8034 Rheology and friction of fault zones (8163)
SC: Nonlinear Geophysics [NG]
MN: Fall Meeting 2005