An aspect of Simi Valley's location, situated beside the Simi Hills, is that it lies in a high-risk area for the wildfires that sweep through Southern California's mountain ranges every few years. Simi Valley is also at risk for earthquakes. The valley is surrounded by faults; the closest ones being the Santa Rosa Fault to the Northwest, the Northridge Hills Fault to the Northeast, and the Chatsworth Fault to the South. In 1994, portions of Simi Valley received significant damage from the Northridge earthquake. See Nuclear Accident at SSFL for information on the accident and associated risk(s) to residents.