How do I find fault or hazard maps for California?

An online map of faults that includes California can be found in the Faults section of the Earthquake Hazards Program website. Choose the Interactive Fault Map, or download KML files and GIS shapefiles from the links on the page.

USGS seismic hazard maps, data and tools for California and other parts of the United States can be found in the Hazards section of the Earthquake Hazards Program website.

The California Department of Conservation, Division of Mines and Geology has a number of Geologic Maps and Data including:

  • Geologic Map of California
  • Alquist-Priolo Earthquake Fault Zone Maps
  • Seismic Hazard Zone Maps
  • Landslide Maps
  • Watershed Maps
  • Topographic Maps 

Related Content

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Where are the fault lines in the Eastern United States (east of the Rocky Mountains)?

Faults are different from fault lines. A fault is a three-dimensional surface within the planet Earth. At the fault, rocks have broken. The rocks on one side of the fault have moved past the rocks on the other side. In contrast, a fault line is a line that stretches along the ground. The fault line is where the fault cuts the Earth's surface...

Why are there so many faults in the Quaternary Faults Database with the same name?

Many faults are mapped as individual segments across an area. These fault segments are given a different value for name, number, code, or dip direction and so in the database each segment occurs as its own unique entity. For example, the San Andreas Fault has several fault segments, from letters a to h, and fault segment 1h has segments with age...

Why are there no faults in the Great Valley of central California?

The Great Valley is a basin, initially forming some ~100 million years ago as a low area between the subducting ocean plate on the west (diving down under the North American plate) and the volcanoes to the east (now the Sierra Nevada mountains). Since its formation, the Great Valley has continued to be low in elevation. Starting about 15 million...

Why are there so many earthquakes and faults in the Western United States?

This region of the United States has been tectonically active since the supercontinent Pangea broke up roughly 200 million years ago, and in large part because it is close to the western boundary of the North American plate. Since the formation of the San Andreas Fault system 25-30 million years ago, the juxtaposition of the Pacific and North...

What is a "Quaternary" fault?

A Quaternary fault is one that has been recognized at the surface and which has moved in the past 1,600,000 years, a portion of the Quaternary epoch.

Where can I find a fault map of the US? Is one available in GIS format?

An online map of US Quaternary Faults is available via the Quaternary Fault and Fold Database . There is an interactive map application to view the faults online and a seperate database search function. KML (Google Earth-type) files and GIS shape files are also available for download from the site. The interactive map provides detailed reports for...

What is a fault and what are the different types?

A fault is a fracture or zone of fractures between two blocks of rock. Faults allow the blocks to move relative to each other. This movement may occur rapidly, in the form of an earthquake - or may occur slowly, in the form of creep . Faults may range in length from a few millimeters to thousands of kilometers. Most faults produce repeated...

What is the relationship between faults and earthquakes?  What happens to a fault when an earthquake occurs?

Earthquakes occur on faults - strike-slip earthquakes occur on strike-slip faults, normal earthquakes occur on normal faults , and thrust earthquakes occur on thrust or reverse faults. When an earthquake occurs on one of these faults, the rock on one side of the fault slips with respect to the other. The fault surface can be vertical, horizontal,...
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Date published: December 7, 2007

Debris Flow Hazard Maps for Southern California Released

Maps showing the potential for destructive mudflows in the wake of recent Southern California wildfires were made available to the public and emergency responders today by the U.S. Geological Survey (USGS). 

The maps estimate the size of potential debris flows, commonly known as mudflows, and the areas that could be affected when rainfall begins on recently-burned areas. 

Date published: March 9, 2006

A Virtual Tour of the Hayward Fault

The U.S. Geological Survey has a new website that offers a virtual tour of the Hayward fault.

Date published: January 11, 2005

USGS Release Updated Landslide Hazard Maps for Southern California

At 6 p.m. Pacific Standard Time, the U.S. Geological Survey advised state and federal agencies about the continuing possibility of landslides and debris flows in seven counties of southern California. The counties are: San Diego, Riverside, Orange, San Bernardino, Ventura, Los Angeles, and Santa Barbara. Here is the advisory that was issued:

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3D perspective view of the likelihood that each region of California will experience a magnitude 6.7 within 30 years
April 20, 2016

3D likelihood California earthquake in the next 30 years

Three-dimensional perspective view of the likelihood that each region of California will experience a magnitude 6.7 or larger earthquake in the next 30 years (6.7 matches the magnitude of the 1994 Northridge earthquake, and 30 years is the typical duration of a homeowner mortgage).

Shaded relief image of the Santa Rosa area showing active faults
April 14, 2016

Santa Rosa area showing active faults

Shaded relief image of the Santa Rosa area showing active faults (black lines) and the detailed rupture pattern of the Rodgers Creek Fault where it crosses central Santa Rosa (in red). The orange, bean-shaped area represents the dense, magnetic body of rock on the east side of the fault beneath Santa Rosa. This body of rock may be largely responsible for the pattern of

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April 14, 2009

Hayward Fault - A virtual tour demonstration

A virtual tour of the 1868 Hayward Earthquake in Google Earth.

Image: Utilities on San Andreas Fault
October 10, 2008

Utilities on San Andreas Fault

Directly on the San Andreas with high pressure gas lines underground and high voltage power lines overhead at Cajon Pass, CA

Attribution: Natural Hazards
USGS
June 19, 2008

What is a landslide hazard map?

Listen to hear the answer.

Image: Liquefaction in Subsurface Layer of Sand
October 17, 1989

Liquefaction in Subsurface Layer of Sand

Ground shaking triggered liquefaction in a subsurface layer of sand, producing differential lateral and vertical movement in a overlying carapace of unliquified sand and silt, which moved from right to left toward the Pajaro River. This mode of ground failure, termed "lateral spreading," is a principal cause of liquefaction-related earthquake damage.

 location of and evidence for recent movement on active fault traces within the Hayward Fault Zone, California

Traces of the Hayward Fault, California

The purpose of this map is to show the location of and evidence for recent movement on active fault traces within the Hayward Fault Zone, California.  The mapped traces represent the integration of the following three different types of data: (1) geomorphic expression, (2) creep (aseismic fault slip),and (3) trench exposures. 

Attribution: Natural Hazards
Map of known active geologic faults in the San Francisco Bay region

Map of known active geologic faults in the San Francisco Bay region

Map of known active geologic faults in the San Francisco Bay region, California, including the Hayward Fault.  The 72 percent probability of a magnitude (M) 6.7 or greater earthquake in the region includes well-known major plate-boundary faults, lesser-known faults, and unknown faults.  The percentage shown within each colored circle is the probability that a M 6.7 or

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