HR: 16:00h
AN: G44A-01 INVITED     [Abstracts]
TI: Repeating Earthquake and Nonvolcanic Tremor Observations of Aseismic Deep Fault Transients in Central California.
AU: * Nadeau, R M
EM: nadeau@seismo.berkeley.edu
AF: Berkeley Seismological Laboratory, 215 McCone Hall, University of California, Berkeley, CA 04720 United States
AU: Traer, M
EM: mtraer@seismo.berkeley.edu
AF: Berkeley Seismological Laboratory, 215 McCone Hall, University of California, Berkeley, CA 04720 United States
AU: Guilhem, A
EM: aurelieguilhem@yahoo.fr
AF: Laboratoire de Gologie de l'Ecole Normale Suprieure, 24, rue Lhomond, 75231, Paris, Cedex 05 France
AB: Seismic indicators of fault zone deformation can complement geodetic measurements by providing information on aseismic transient deformation: 1) from deep within the fault zone, 2) on a regional scale, 3) with intermediate temporal resolution (weeks to months) and 4) that spans over 2 decades (1984 to early 2005), including pre- GPS and INSAR coverage. Along the San Andreas Fault (SAF) in central California, two types of seismic indicators are proving to be particularly useful for providing information on deep fault zone deformation. The first, characteristically repeating microearthquakes, provide long-term coverage (decades) on the evolution of aseismic fault slip rates at seismogenic depths along a large (~175 km) stretch of the SAF between the rupture zones of the ~M8 1906 San Francisco and 1857 Fort Tejon earthquakes. In Cascadia and Japan the second type of seismic indicator, nonvolcanic tremors, have shown a remarkable correlation between their activity rates and GPS and tiltmeter measurements of transient deformation in the deep (sub-seismogenic) fault zone. This correlation suggests that tremor rate changes and deep transient deformation are intimately related and that deformation associated with the tremor activity may be stressing the seismogenic zone in both areas. Along the SAF, nonvolcanic tremors have only recently been discovered (i.e., in the Parkfield-Cholame area), and knowledge of their full spatial extent is still relatively limited. Nonetheless the observed temporal correlation between earthquake and tremor activity in this area is consistent with a model in which sub-seismogenic deformation and seismogenic zone stress changes are closely related. We present observations of deep aseismic transient deformation associated with the 28 September 2004, M6 Parkfield earthquake from both repeating earthquake and nonvolcanic tremor data. Also presented are updated deep fault slip rate estimates from prepeating quakes in the San Juan Bautista area with an assessment of their significance to previously reported quasi-periodic slip rate pulses and small to moderate magnitude (> M3.5) earthquake occurrence in the area.
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 8107 Continental neotectonics (8002)
SC: Geodesy [G]
MN: Fall Meeting 2005