The Greenville Fault: Preliminary Estimates of Its Long-Term Creep Rate and Seismic Potential

Once assumed to be locked, we show that the northern third of the Greenville fault (GF) creeps at 2 mm/yr, based on 47 yr of trilateration net data. This northern GF creep rate equals its 11 ka slip rate, suggesting a low strain accumulation rate. In 1980, the GF, easternmost strand of the San Andreas fault system east of San Francisco Bay, produced an M-w 5.8 earthquake with a 6 km surface rupture and dextral slip growing to >= 2 cm on cracks over a few weeks. Trilateration shows a 10 cm post-1980 transient slip ending in 1984. Analysis of 2000-2012 crustal velocities on continuous Global Positioning System stations, allows creep rates of similar to 2 mm/yr on the northern GF, 0-1 mm/yr on the central GF, and similar to 0 mm/yr on its southern third. Modeled depth ranges of creep along the GF allow 5%-25% aseismic release. Greater locking in the southern two-thirds of the GF is consistent with paleoseismic evidence there for large late Holocene ruptures. Because the GF lacks large (> 1 km) discontinuities likely to arrest higher (similar to 1 m) slip ruptures, we expect full-length (54 km) ruptures to occur that include the northern creeping zone. We estimate sufficient strain accumulation on the entire GF to produce Mw 6.9 earthquakes with a mean recurrence of similar to 575 yr. While the creeping 16 km northern part has the potential to produce an M-w 6.2 event in 240 yr, it may rupture in both moderate (1980) and large events. These two-dimensional-model estimates of creep rate along the southern GF need verification with small aperture surveys.