Detailed kinematics, structure and recurrence of micro-seismicity in the SAFOD target region

Abstract

Large numbers of small earthquakes recorded over 2 decades and analyzed with advanced techniques are used to characterize the detailed kinematics, structure and recurrence interval scaling properties of micro-seismicity in a 4 × 4 km lateral and 6 km deep crustal volume encompassing the region of the SAFOD deep drilling experiment. The characterization reveals 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 region, ∼55% of the earthquakes are members of 52 characteristically repeating earthquake sequences. The recurrence intervals of the repeating target events are consistent with the interval scaling of the other sequences. However this. scaling is contrary to that expected from standard constant stress-drop theory. Copyright 2004 by the American Geophysical Union.