Earthquake effects on SDG&E's 500/230kV Imperial Valley Substation

On April 4, 2010, at 03:40 PM, an earthquake measuring 7.2 Mw on the Moment Magnitude scale occurred in the Baja California, Mexico area. The total duration of the earthquake was about 40 seconds. The earthquake, referred to as the Sierra El Mayor Earthquake (aka Mexicali Earthquake), occurred along the Laguna Salada Fault in Mexico which is a segment of the Elsinore Fault System. The epicenter of the earthquake was 40 miles southeast from the Imperial Valley (IV) Substation, and fault ruptures occurred as close as 9 miles from IV Substation. A maximum acceleration pulse of 0.29g occurred in the area of IV Substation. This information was obtained from the United States Geological Survey (USGS) and a report prepared by San Diego Gas & Electric's (SDG&E's) geotechnical consultant, United Research Services Corporation (URS).