HR: 1340h
AN: T13A-1339    [Abstracts]
TI: Structure, Kinematics and Recurrence of Microseismicity in the SAFOD Target Region
AU: * Uhrhammer, R A
EM: bob@seismo.berkeley.edu
AF: Berkeley Seismological Laboratory, 215 McCone Hall University of California, Berkeley, CA 94720-4760 United States
AU: Nadeau, R M
EM: nadeau@seismo.berkeley.edu
AF: Berkeley Seismological Laboratory, 215 McCone Hall University of California, Berkeley, CA 94720-4760 United States
AU: Dolenc, D
EM: dolenc@seismo.berkeley.edu
AF: Berkeley Seismological Laboratory, 215 McCone Hall University of California, Berkeley, CA 94720-4760 United States
AU: Michelini, A
EM: michelini@ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata, 605, Rome, 00143 Italy
AU: McEvilly, T V
EM: tom@seismo.berkeley.edu
AF: Berkeley Seismological Laboratory, 215 McCone Hall University of California, Berkeley, CA 94720-4760 United States
AB: Large numbers of small earthquakes recorded over 2 decades and analyzed with advanced techniques are used to characterize the detailed structure and kinematics of the fault and the recurrence interval scaling properties of repeating micro-seismicity in a 4 x 4 km lateral and 6 km deep crustal volume surrounding the SAFOD experiment's deep drilling zone. The characterizations reveal that the seismically active San Andreas fault in the vicinity of SAFOD's repeating magnitude 2 target earthquakes is composed of two sub-parallel fault strands that are creeping at comparable rates and that one of the strands lies between the SAFOD drilling platform and SAFOD's target events. In the study region, $\sim$ 50 % of the earthquakes are members of 52 characteristically repeating earthquake sequences. The recurrence properties of the two repeating target event sequences are also characterized and are found to be consistent with the recurrence scaling of the other sequences in the study zone. This scaling, however, is contrary to that expected from standard constant stress-drop theory. SAFOD's 'in-situ' measurements of fault zone processes and its near-field seismic observations of repeating M2 earthquake sequences should provide the information needed to resolve the apparent discrepancy between the observed and expected microearthquake recurrence behavior.
DE: 8010 Fractures and faults
DE: 8107 Continental neotectonics
DE: 7200 SEISMOLOGY
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting