Images

An automobile lies crushed under the third story of this apartment building in the Marina District. The ground levels are no longer visible because of structural failure and sinking due to liquefaction.

A downtown building at the corner of Alice and 13th Streets lost part of its unreinforced facade and brick masonry.

The segments of the San Andreas Fault, and the probability for strong shaking in the next 30 years on each segment. 

Oblique aerial view of San Andreas Fault (between white arrows) in southeastern Coachella Valley, near Red Canyon; view to the west.

During the first week of April a different type of seismic signature was showing up on seismograms from Mount St. Helens. On April 1 the first weak harmonic tremor was detected. Stronger bursts of harmonic tremor were recorded on the 2nd. The seismogram above is an example of harmonic tremor recorded at seismic station RAN on April 2.

The nine generalized couples of the seismic moment tensor. Modified after Aki and Richards (1980).

Charles Richter, inventor of the Richter Scale.

Seismology is the study of earthquakes and the structure of the earth, by both naturally and artificially generated seismic waves.

Photo of deformed rock. Deformation is a change in the original shape of a material. When we are talking about earthquakes, deformation is due to stress and strain.

The Richter magnitude scale was developed in 1935 by Charles F. Richter of the California Institute of Technology as a mathematical device to compare the size of earthquakes. The magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs.

Photo of 1995 landslide in La Conchita, California. A landslide is a movement of surface material down a slope. 

1906 earthquake damage to home on Howard and 17th Streets in San Francisco. Liquefaction, the phenomenon of saturated soils losing their stiffness and strength during shaking, caused structures to tilt and collapse.

Strong shaking during the 1868 Hayward Fault earthquake caused the second story of the Alameda County Courthouse in San Leandro to collapse (photo courtesy of the Bancroft Library, University of California). The inset photo shows the courthouse before the quake

A Cessna Grand Caravan airplane took measurements over Virginia's Louisa, Goochland and Fluvanna counties. The data collected will help USGS scientists locate buried geologic features associated with the August 23, 2011 earthquake and its aftershocks. Surveys were conducted from 7/15- 7/25.

A Cessna Grand Caravan airplane took measurements over Virginia's Louisa, Goochland and Fluvanna counties. The data collected will help USGS scientists locate buried geologic features associated with the August 23, 2011 earthquake and its aftershocks. Surveys were conducted from 7/15- 7/25.

A Cessna Grand Caravan airplane took measurements over Virginia's Louisa, Goochland and Fluvanna counties. The data collected will help USGS scientists locate buried geologic features associated with the August 23, 2011 earthquake and its aftershocks. Surveys were conducted from 7/15- 7/25.

Damage to a house in Louisa County, Virginia, after a magnitude 5.8 earthquake on August 23, 2011.

Damage to a house in Louisa County, Virginia, after a magnitude 5.8 earthquake on August 23, 2011.

Life in a tent. Family members having lunch together.

Blue tents in Longmen near epicenter.

Life in a tent. A grandfather taking the baby outside the tent. The wall with shear crack behind him was their house which suffered serious damage.

Geologists examine an exposure of a tidal marsh bank on Sitkinak Island, Alaska. The bank exposes interbedded peat and silt that records sudden vertical land movements associated with megathrust fault slip during large earthquakes.