Borrego
Mountain - uplifted ridge of granite between two strands of
the San Jacinto fault arranged in a restraining overstep. Double-headed
arrows indicate relative displacement of main blocks that bound the shear
couple that is indicated by the single-headed arrows. Lines at each
end of the block are inferred. Lines across the block are faults,
all but one of which are normal faults arranged properly for right simple
shear. The two bounding faults each slipped about 1/2 meter right
laterally during the 1968 Borrego Mountain earthquake (M 6.8).
Photographed 1986 and Copyrighted by Arthur G. Sylvester