Abstract

Geologic and geodetic studies were made in the area of Camp Parks, a site proposed for a 4600-ft-diameter, circular, 200-BeV proton accelerator in the western portion of the Liver-more Valley. The area is underlain by Pliocene sediments of the Orinda formation and by Quater­nary alluvium, and is transected by the Calaveras, Pleasanton, and Parks faults. The expression of the Pleasanton faults in the alluvial surface suggests that the area is presently undergoing active tectonism.

A geodetic network, established in 1964 in co-operation with the U. S. Coast and Geodetic Survey, combined precise leveling across the western Livermore Valley and precise horizontal measurements across the Pleasanton and Calaveras faults. A previously installed large-area triangulation network encompassing the Livermore Valley was reobserved; there were no significant changes of position since 1947–1948. Reobservation of the 1964 network one year later showed the development of a subsidence basin in the southern San Ramon Valley with vertical differences on the order of 0.05 ft, consistent clockwise horizontal movement across the Pleasanton faults, and an apparent thrusting movement across the Calaveras fault. Though the directions of hori­zontal movement are meaningful, the magnitudes of displacement are questionable, since only one year elapsed between measurements. It is considered that subsidence in response to with­drawal of ground water is superimposed on tectonic movements.

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