The thermal and mechanical behavior of faults.

摘要

Fault behavior is controlled to a large degree by the geometry and frictional properties of faults. Using a combination of field observations and modeling of fault systems throughout California, I discuss these different factors affecting the thermal and mechanical behavior of faults.; Field observations of strike slip faults in the central Sierra Nevada, California, combined with a mechanical analysis of fault interaction, show that a cluster of small faults flanking the tip of a large fault zone will tend to diffuse the stress concentration near the fault zone tip, thus inhibiting its ability to link and grow.; Observations of surface deformation allow us to determine the geometry and kinematics of faults in the San Francisco Bay Area. I present a new compilation of over 200 horizontal surface velocities collected using Global Positioning System observations from 1993--2003. I interpret this velocity field using a 3-D block model to determine the relative contributions of block offset, elastic strain accumulation, and shallow aseismic creep.; Large earthquakes generate frictional heat, and the magnitude of heating is related the frictional strength of the fault. I present apatite fission-track (AFT) analyses of samples from the San Gabriel fault zone in southern California. There is no evidence of a localized thermal anomaly, indicating that either there has never been an earthquake with >4 m of slip at this locality or the average apparent coefficient of friction is 0.4.; The San Andreas Fault Observatory at Depth Pilot Hole traverses the upper 2 km of a site 1.8 km west of the San Andreas fault (SAF) near Parkfield, California. To evaluate the burial and exhumation history of the site in relation to the kinematics and mechanics of the SAF, I present AFT and (U-Th)/He analyses from Pilot Hole samples. There has been 1.5 km of total vertical motion adjacent to the SAF since ∼60 Ma.; Numerical models show that faults with hetergeneous frictional asperities produce heat flow patterns that are asymmetric across the fault as well as along-strike. This asymmetry has implications for conclusions about fault strength drawn from existing heat flow measurements.