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.
Photographic archive collection from the USGS Photo Library. Photos dated 1868-1992 are of geology, earthquake damage, national parks, pioneer photographers, St. Helens eruption and mining and available at 100, 700 and 1400 dots/inch resolution.
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.
Homepage for a paleoseismic field study of the geologic record of prehistoric earthquakes in the Puget Lowland region to evaluate seismic hazards with links to an atlas and reports on historic earthquakes in the Washington and Oregon area.
Online booklet on the San Andreas fault system on the California coastal region with discussion of faults, relationship of faults and earthquakes, magnitude of earthquakes, and earthquake probability.
Homepage for the Southern California Integrated GPS Network (SCIGN) Pasadena Field Office involved in operating GPS stations, data recording, and supplying of earthquake data. Links to GPS data analysis, photos, and technical information.