The Landers / Big Bear Earthquakes of June 28, 1992 (Image 2 of 20)

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.