| Deformation associated with faults is localized along discontinuities at a variety of scales, both in time and space. Relative displacements across m-scale, left-lateral strike-slip faults in the Lake Edison Granodiorite are transferred between segments by ductile shearing at right steps, and by extensional fracturing at left steps. The structures associated with fault terminations change from dilatant splay fractures only, to splay fractures and ductile fabrics on opposing sides of the fault, to ductile fabrics ahead of the fault with increased temperatures. The local magnitudes and spatial distributions of the maximum tensile stress, the mean stress, and the maximum shear stress correlate with the distributions of different deformation mechanisms.;Fault slip distributions are commonly assumed to be symmetrical about a central slip maximum. Analytically and numerically computed fault-slip distributions indicate that (1) changes in the (frictional) strength along a fault, (2) spatial gradients in the stress field, and (3) inelastic deformation near fault terminations can cause deviations from symmetrical distributions. In particular, the interaction of faults is expected to strongly influence slip gradients.;The southern Santa Cruz Mountains (SCM) are closely associated with a left bend along the San Andreas fault. Six samples from a transect across the Loma Prieta area yield apatite fission track ages that suggest that about 3 km of unroofing has occurred over the last 4.6 ;Strain transients following large earthquakes may be responsible for clustering of seismic events in space and time. The post-seismic velocity field in the epicentral region of the 1989 Loma Prieta earthquake differs significantly from displacement rates measured before the event. Oblique reverse slip at a rate of 8 cm/yr on a sub-vertical fault and reverse slip at a rate of 6 cm/yr on a thrust fault of the FTS can explain the observed motions. Rapid post-earthquake fault slip may be a precursory phenomenon to impending rupture. |
