Southern California Earthquake Data Center

Significant Earthquakes and Faults

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Fault Name Index

Clamshell - Sawpit Canyon Fault

Type of Fault: reverse
Length: 18 km
Nearby Communities: Sierra Madre, Monrovia
Most Recent Surface Rupture: Late Quaternary
Other Notes: This fault dips to the north at about 40 (at the surface) to 50 (at depth) degrees.


The Sierra Madre earthquake of 1991 probably originated on the Clamshell - Sawpit Canyon fault. Though a sizable earthquake, the depth of this quake prevented the rupture from reaching the surface.



This fault is featured on the following maps:
Mojave Fault Map
Southern Fault Map
Los Angeles Fault Map