Copyright Information: All images are in the public domain and available for free. If you use this image, credit NOAA/NGDC, Lindie Brewer, U.S. Geological Survey. |
This figure shows a soil failure adjacent to the Santa Ana River near the epicenter of the Big Bear earthquake. Light colored tan sand lies on top of the gray soil on the cracked road bed. These secondary cracks produced by earth shaking were found near the entrance to the South Fork campground, on slopes and in the stream embankments. There were no reports of a primary ground rupture in connection with the Big Bear earthquake. Such soil failures (liquefaction) as depicted here occur when ground water near the surface is forced between the grains of sand during an earthquake. The sandy soil behaves like a very thick liquid. The eruption of liquefied sediment is facilitated by fissures in the ground. Image Credit: Lindie Brewer. U.S. Geological Survey June 28, 1992 Landers and Big Bear USA earthquake Southern California residents were rudely awakened Sunday morning June 28, 1992 at 04:57 am (June 28 at 11:57 GMT), by an earthquake of magnitude 7.6 (Ms) followed by a smaller 6.7 (Ms) magnitude earthquake about three hours later (June 28 at 15:05 GMT). The largest shock occurred approximately 6 miles southwest of Landers, California and 110 miles east of Los Angeles. The second earthquake was entered approximately 8 miles southeast of Big Bear City in the San Bernardino Mountains near Barton Flats. A distance of 17 miles and 7,000 feet in elevation separate the two earthquake locations. Event Data:
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