Chronological Earthquake Index
Fish Creek Mountains Earthquake
TYPE OF FAULTING: right-lateral strike-slip (?)
TIME: October 21, 1942 / 9:30 am, PWT (PWT = Pacific War Time, and is equivalent to Pacific Daylight Savings Time)
LOCATION: 32° 58' N, 116° 00' W about 45 km (28 miles) west of Brawley about 95 km (60 miles) east of San Diego
The Fish Creek Mountains earthquake occurred on the southern section of the CoyoteCreek fault, the southernmost section of the San Jacinto fault zone, in a fairly remote area of southern California. Thus, it caused relatively little damage for its size. However, it was felt over a large area of southern California, as well as parts of Baja California and Arizona. The quake caused rockslides in Carrizo Gorge, blocking Highway 80 and the San Diego & Arizona Eastern Railroad. It caused minor damage in Brawley, El Centro, Westmoreland, and even San Diego, where at least 40 aftershocks were reported felt in the following eight days. Hardest hit was Jacumba Hot Springs, fairly close to the epicenter, but even there, damage was moderate. No surface rupture was reported in association with this earthquake.
In recent years, it has been suggested that the Fish Creek Mountains quake actually occurred on a northeast-trending left-lateral fault within the San Jacinto fault zone, rather than on the primary right-lateral fault. This would make it similar to the Elmore Ranch earthquake of 1987 on the Elmore Ranch fault, a left-lateral fault conjugate to the right-lateral Superstition Hills fault, often considered to be a southeast extension of the San Jacinto fault zone.