Chronological Earthquake Index
Lytle Creek Earthquake
TIME: September 12, 1970 / 7:31 am PDT
LOCATION: 34° 16.2' N, 117° 32.4' W 24 km (15 miles) northwest of San Bernardino about 67 km (42 miles) ENE of Los Angeles
DEPTH: roughly 9 km
Twenty minutes after a magnitude 4.1 "foreshock" (which was actually in a slightly different location), the Lytle Creek earthquake struck the area near Cajon Pass, knocking a San Bernardino radio station off the air, and causing landslides and rockfalls in the Transverse Ranges. Several roads were blocked or partially blocked. The quake caused some unusual damage in areas a fair distance from the epicenter. Power was disrupted in the Santa Monica Mountains northwest of Hollywood. A high-pressure water system in a Riverside aerospace plant was damaged, leading to a subsequent boiler explosion that injured four people. More typical minor damage also occurred, primarily in the Lytle Creek area (intensity VII on the Modified Mercalli Scale) and to a lesser degree in the nearby towns of Colton, Crestline, Cucamonga, Fontana, Glendora, Highland, Mt. Baldy, Rialto, Rubidoux, and Wrightwood.
Though ultimately a forgettable event, and certainly overshadowed by the San Fernando (Sylmar) Earthquake which followed five months later, the Lytle Creek quake did get the attention of much of southern California -- it was felt strongly as far away as Barstow, Mojave, Oxnard, and Palm Springs, and even caused tall buildings to sway in downtown San Diego.