Ground shaking caused by the sudden release of accumulated strain by an abrupt shift of rock along a fracture in the earth or by volcanic or magmatic activity, or other sudden stress changes in the earth.
Information on earthquakes in central California and the San Francisco region with links to four types of field studies, deep seismic investigations, geotechnical investigations, shallow seismic imaging, and airborne geophysical surveys.
After the powerful earthquake of April 18, 1906, staff of the U.S. Geological Survey stationed in Sacramento and Berkeley brought help to the residents of devastated San Francisco, documented the effects of the quake, and investigated its causes.
If you live or work in the San Francisco Bay region, this handbook explains why you should be concerned with earthquakes, what you can expect during and after a quake, and what you need to do beforehand to be safe and reduce property damage.
Fact sheet describing plans for a San Andreas Fault Observatory at Depth (SAFOD) by drilling into the fault to install instruments for long-term monitoring near the location of the magnitude 6 Parkfield earthquakes.
Overview of volcano hazards in California with links to monitoring data including earthquakes and deformations, long-term outlook, volcano hazards in the area, USGS response plan, image gallery, monitoring and topical studies, publications and references.
Description of earthquake that was felt in Joshua Tree region (1999) and links to earthquake summary, shaded relief map, aerial photos of the rupture zone, shaking intensity maps, damage reports, and seismograph network map.
Study of the probability of a major earthquake in San Francisco Bay region with colored map and links to relevant publications. Text also available in PDF format and graphic available in Illustrator or Photoshop format.
Describes the monitoring effort and provides real-time data of the current restless activity of the caldera, including earthquakes, ground deformation, and release of volcanic gas and plus link to volcano monitoring techniques.
Links to geologic information on western states: Alaska, Arizona, California, Hawaii, Idaho, Nevada and Oregon including information on coastal and marine geology, mineral resources, earthquakes, landslides, earthquake hazards and geologic maps.