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A study was conducted to investigate thermobarometric and compositional nature of upper mantle and lower crust xenoliths located in Coyote Lake alkali basalts near the Coyote lake Reservoir. These rocks are bounded on the east and west by the Calaveras and Coyote Creek faults, respectively. Petrologic and geophysical observations indicate that deep fault extensions exist in the Calaveras Fault zone likely penetrating a large part if not the entire lithosphere during the Pliocene period. The study provided a chance to probe the magmatic mantle rocks beneath the San Andreas Fault system.

A complex structural and metamorphic history is shown by the Orocopia Schist. The overwhelming trend away from the Orocopia fault is nearly NE-SW reflecting the early phase of deformations during subduction. Possible fold formations and times, and a possible detachment faulting during the Tertiary are dsicussed as possible reasons for the regions unique geological status.

The Coast Ranges from the range front on the east to the continental margin on the west in Central Valley, CA, exhibit a sudden transition along the deformed mountains and less deformed ones. The less deformed structures constitute the California valley. The Coast Ranges of California exhibit major thrusts and faults in the mountain regions.

A study of the accumulation of sediments on both sides of the Santa Susana Fault show Saugus and Pacoima formations were deposited from about 2.3 to 0.5 Ma. The Pacoima formations overlap the Saugus formations in the east Ventura basin. The presence of the 0. 76 Ma Bishop ash and magnetostratigraphy of Saugus and Pacoima strata reveals that the average sedimentation rate is 0.9 km/m.y. in the east Ventura basin and 1.1 km/m.y. in the northern San Fernando Valley. The accumulation of sediments on Santa Susana Fault has raised Santa Susana Mountains.

Time-depth constraints on intrusion and unroofing during the Miocene are revealed by cooling age patterns and geobarometric data from the Black Mountains in Death Valley, California. Northwest diachronous cooling withdike intrusion show decreasing ages, suggesting a 10-15 km denudation along a northwest-oriented detachment system, with an average initial dip of 20 degress Footwall flexure migration under a scoop-shaped hanging wall block explains this northwestward unroofing and dike intrusion. A signifcant conclusion is that middle crust ductile fabrics steepen during unloading in the upper crust.

The Del Puerto ophiolite in the northern Diablo Range, California is overlain by fault displacement-sheared Fransiscan metagraywacke. Coast Range ophiolite and Great Valley sequence attentuation was concurrent with the normal faulting and extensional offset representing the displacement. Moving westward across the underlying oceanic plate, the Fransiscan Complex lengthened and thinned due to subduction-caused instability. These movements resulted in blueschist facies alongside only slightly-metamorphic hanging wall units.

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.