The new disaster film, 'San Andreas', has put the major Californian fault in the spotlight.
But a new study has found it isn't just the San Andreas fault we should be worried about; a very real threat of earthquakes and tsunamis lurks offshore Southern California.
Researchers say that several long faults could cause magnitude 8.0 quakes and tsunamis within 90 miles (145km) of the coast.
The blocks are wedged together all the way from the San Andreas Fault on the east, to the edge of the continental shelf on the west, from 90 to 125 miles (150 to 200km) offshore.
These chunks of crust get squeezed and rotated as the Pacific plate slides northwest, away from California, relative to the North American plate.
The mostly underwater part of this region is called the California Continental Borderland, and includes the Channel Islands.
California has a seven per cent chance of experiencing an earthquake of magnitude 8 or larger over the next three decades, U.S. government scientists said in March.
The seven per cent probability is based on new modeling, the United States Geological Survey said in a new study. Previously, scientists estimated the probability for such a quake at 4.7 percent over 30 years.
'We are fortunate that seismic activity in California has been relatively low over the past century,' said Tom Jordan, Director of the Southern California Earthquake Center and a co-author of the study.
'But we know that tectonic forces are continually tightening the springs of the San Andreas fault system, making big quakes inevitable.'
The new modeling system takes into account shaking that might occur on several different faults, rather than looking at each rupture as a separate incident, said Ned Field, the lead author of the USGS report.
An earthquake of magnitude 8 or larger is capable of devastating large areas, the USGS said.