section_path: Geography/Geology
section_name: Geology
paragraph_text: Geology
  
  Los Angeles is subject to earthquakes because of its location on the Pacific Ring of Fire. The geologic instability has produced numerous faults, which cause approximately 10,000 earthquakes annually in Southern California, though most of them are too small to be felt. The strike-slip San Andreas Fault system, which sits at the boundary between the Pacific Plate and the North American Plate, passes through the Los Angeles metropolitan area. The segment of the fault passing through Southern California experiences a major earthquake roughly every 110 to 140 years, and seismologists have warned about the next "big one", as the last major earthquake was the 1857 Fort Tejon earthquake. The Los Angeles basin and metropolitan area are also at risk from blind thrust earthquakes. Major earthquakes that have hit the Los Angeles area include the 1933 Long Beach, 1971 San Fernando, 1987 Whittier Narrows, and the 1994 Northridge events. All but a few are of low intensity and are not felt. The USGS has released the UCERF California earthquake forecast, which models earthquake occurrence in California. Parts of the city are also vulnerable to tsunamis; harbor areas were damaged by waves from Aleutian Islands earthquake in 1946, Valdivia earthquake in 1960, Alaska earthquake in 1964, Chile earthquake in 2010 and Japan earthquake in 2011.