Paleoseismic Investigation of the San Gorgonio Pass Fault Zone Near Cabazon, California

Paleoseismic Investigation of the San Gorgonio Pass Fault Zone Near Cabazon, California
Author: Shahid Ramzan
Publisher:
Total Pages: 63
Release: 2012
Genre: Earthquakes
ISBN:

The discontinuous nature of the San Andreas fault at San Gorgonio Pass has led to competing models about whether or not large earthquakes can rupture through this structurally complex region. To test these models the author excavated trenches across the San Gorgonio Pass fault zone (SGPFZ) near Cabazon as part of a larger effort. The trench site is located ~100 m to the east of a site excavated in 1997 by Yule where trenches uncovered evidence for at least one earthquake 500-700 yrs ago. At the 1997 site, extensive bioturbation and low sedimentation rates hampered efforts to distinguish events. The new site, located where two alluvial fans merge, was selected for its higher sedimentation rates and excellent stratigraphy. Evidence from Cabazon supports a model with infrequent ruptures (by San Andreas fault standards) in San Gorgonio Pass and rare through-going events.