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Data from geotechnical boreholes and trenches, in combination with geomorphologic mapping, indicate that the Hollywood fault is an oblique, reverse-left-lateral fault that has undergone at least one surface-rupturing earthquake during latest Pleistocene to middle or late Holocene time. Geomorphologic observations show that the fault extends for 14 km along the southern edge of the eastern Santa Monica Mountains, from the Los Angeles River westward through downtown Hollywood to northwestern Beverly Hills, where the locus of active deformation steps 1.2 km southward along the West Beverly Hills lineament to the Santa Monica fault. Rupture of the entire Hollywood fault, by itself, could produce a [M.sub.w] [approximately]6.6 earthquake, similar in size to the highly destructive, 1994 Northridge earthquake, but even closer to more densely urbanized areas. Assuming a 0.35 mm/yr minimum fault-slip rate consistent with available geologic data, we calculate an average maximum recurrence interval for such moderate events of [less than or equal to][approximately]4000 yr. Although occurrence of such moderate events is consistent with the elapsed time since the poorly constrained age of the most recent surface rupture, the data do not preclude a longer quiescent interval suggestive of larger earthquakes. If earthquakes much larger than [M.sub.w] [approximately]6.6 occurred in the past, we speculate that they may have been generated by the Hollywood fault together with other faults in the Transverse Ranges Southern Boundary fault system.

An earthquake that occurred in Petrolia, California, on Apr. 25, 1992, is a subduction process between the Gorda deformation zone and the Humboldt plate in the Cape Mendocino region. This result is obtained from the slip direction, N75 deg E - N 80 deg E, of the mainshock and aftershock distribution of the quake. The processes involved in the quake and the two large aftershocks and a description of seismotectonics of the region are given.

Timing of the latest movement on the Santa Cruz Island fault, a dramatic physiographic feature of the southern boundary of the California Transverse Ranges, is demonstrated to be latest Pleistocene to Holocene in age. Faulting of dated terrace gravels confirms that the most recent rupture on the fault is not older than 11.78 [+ or -]0.1 ka. This represents an order of magnitude increase over the recency suggested by previous work and requires proportional increases in estimates of the minimum slip rate and seismic hazard posed by the fault. Uplifted lates Pleistocene to Holocene fill terraces are consistent with models of high rates of uplift and high sediment supply. Numerical solution of the interaction of sea-level rise with uplift at the west end of Santa Cruz Island predicts that the youngest strata in the faulted terrace sequence are about 6.1 ka. Reevaluation of high-resolution seismic sections just west of the island supports the latest Pleistocene to Holocene timing of the most recent rupture on the fault. The Santa Cruz Island fault apparently represents an active seismogenic element of southern California, the recency and high rate of activity of which have not been previously recognized.

As a result of the October 17, 1989, Loma Prieta (Santa Cruz Mountains, California) earthquake, liquefaction of the fluvia, estuarine, eolian, and beach sediments under a sand spit destroyed the Moss Landing Marine Laboratories and damaged other structures and utilities. Initial studies suggested that the liquefaction was a local phenomenon. More detailed offshore investigations, however, indicate that it occurred over a large area (max. 8 [km.sup.2]) during or shortly after the earthquake with movement of unconsolidated sediment toward and into the head of Monterey submarine canyon. This conclusion is supported by side-scan sonographs, high-resolution seismic-reflection and bathymetric profiles, onshore and a sea-floor photographs, and underwater video tapes. Many distinct lobate features were identified on the shallow shelf. These features almost certainly were the result of the October 17 earthquake; they were subsequently destroyed by winter storms. In addition, fresh slump scars and recently dislodged mud debris were found on the upper, southern wall of Monterey submarine canyon.

An overview is presented on California's San Andreas Fault Observatory at Depth (SAFOD) project, currently underway in the town of Parkfield. A 7,100 ft pilot hole has been drilled for researching seismology in the region. The project is part of EarthScope, a larger project for the study of North American tectonics and geomorphology.

Six successive magnitude 6 earthquakes had occurred at Parkfield, California, on the San Andreas fault, regularly every 21 to 24 years from the middle of the 19th century to 1966. [...]

Research conducted by the Southern California Earthquake Center is presented, which targets areas particularly prone to earthquake damage as a result of specific geological features. These features include the degree of softness of surface rocks and the thickness levels of surface sediments.

Research is presented concerning the three major earthquakes which have taken place in the Gulf of California between April 1969 and June 1995. The influence of faults distinct from oceanic spreading centers on seismic activity in the area is discussed.

Research is presented concerning the movement of the active faults in the southern Cascadia subduction zone in California. The use of geodetic models to predict the seismic hazards associated with the faults is discussed.

Much of the earthquake research conducted in Califorina has focused on measuring recurrence rates for the purposes of prediction. However, very little light has been shed on its causes. In line with this, scientists are planning to drill a hole 10,000 meters down into the San Andreas fault, to study its physics, mineralogy and mechanics. Simulation studies have shown that present knowledge on the process of faulting is insufficient. Only with such knowledge can more effective modeling, and hence, prediction be carried out.