ABSTRACT

The investigators on this project are studying the mechanics of faulting on the Parkfield segment of the San Andreas Fault. Their study looks into the scaling of micro-earthquakes, the relationships between micro-earthquakes and the Mw6.0 Parkfield mainshock and its associated postseismic slip, heterogeneity of stress release, fault strength, and fault rheology. They will use data from the Berkeley High Resolution Borehole Seismic Network and the NSF-funded SAFOR pilot and primary boreholes. They will produce high resolution images of the kinematic rupture processes of these small earthquakes. The results of this study will have direct bearing on fundamental questions concerning the spatial dimensions of small earthquakes, their rupture and slip velocities, the distribution of slip and stress drop and triggering of nearby sequences of earthquakes. An advantage of studying these small events is that recurrence is rapid enough that many cycles may be observed. Thus it will be possible to examine the repeatability of the system. The project will involve graduate and undergraduate students, take advantage of Earthscope data and may help understanding of earthquake occurrence that is useful for earthquake forecast models.

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