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.
Description and photos documenting offsets and 260 km rupture in the Denali glacier in central Alaska after the November 3, 2002 earthquake, the 9th largest earthquake in the United States in the last 200 years.
Description of the seismic monitoring of the active Hawaiian volcanoes with information on the network, instrumentation, and recording stations with links to related information.