On March 25, 1937, a moderately large, moderately strong local earthquake—magnitude 6, maximum ascertained intensity VI of the 1931 scale—occurred in Southern California.
The origin was very nearly equidistant from the stations at (1) La Jolla and Riverside, (2) Mount Wilson and Pasadena, and (3) Santa Barbara and Haiwee; with epicenter at φ = 33°28′ N lat., λ = 116°35′ W long., and origin time O = 08h49m04sa.m., P.S.T. (16h49m04sG.C.T.). The source is very close to the surface outcrop of the San Jacinto fault zone.
The origin was in the midst of a large tract of arid, mountainous country and no significant damage resulted. The shock was large enough and strong enough, however, to have caused much damage had its source been in or near a thickly populated district.