LIQUEFACTION OBSERVATIONS MEXICALI, MEXICO – APRIL 4, 2010 EARTHQUAKE

The M_W 7.2 Sierra El Mayor-Cucapah Earthquake occurred in Northern Baja California, Mexico on April 4, 2010. The epicenter was positioned in the farming communities approximately 30 miles south southeast of Mexicali, Mexico on the western side of a broad flat extensional sedimentary basin known as the Mexicali Valley. A significant effect of the earthquake was widespread liquefaction. Liquefaction features were observed across the Mexicali Valley that included lateral spreading, settlement, ground fissures, sand volcanoes and flooding. Observations after the earthquake noted the presence of loose, saturated, fine sand and non-plastic silts, and a shallow ground water table contributing to the liquefaction. Liquefaction-associated effects on structures included differential settlement, bearing capacity failures and severe lateral spreading damage. Structure types affected included single-story homes to multi-story buildings, irrigation canals, bridges and roads. Impacts from liquefaction included topographic warping of the previous flat farmland and roads and severe damage to lined and unlined irrigation canals. Observations along the Rio Hardy River noted significant lateral spread damage displacements and damage along and adjacent to its banks. Sand volcanoes and sand fissures were scattered across the farm land, and around and in residential structures. The sand volcanoes were described by locals to have shot up to six feet above the ground. Six locations in the Mexicali Valley where significant liquefaction effects were observed will be presented: 1) UABC University Campus; 2) Rio Hardy River ranch; 3) Baseball field in residential area; 4) Farm land; 5) Colorado River bridges; 6) Residential homes.