Images

An oceanic spreading ridge is the fracture zone along the ocean bottom where molten mantle material comes to the surface, thus creating new crust. This fracture can be seen beneath the ocean as a line of ridges that form as molten rock reaches the ocean bottom and solidifies.

Seismicity of the United States 1975-1995. Seismicity refers to the geographic and historical distribution of earthquakes.

This ShakeMap of the January 17, 1994 M6.7 Northridge earthquake shaking shows the result of rupture directivity toward the north.

The Emerson fault, one of the segments that ruptured in the M7.2 1992 Landers, Calfornia earthquake. 

1992 M7.2 Landers, California earthquake slip model

A slip model is a kinematic model that describes the amount, distribution, and timing of slip associated with an earthquake.

Cross-Sections of Seismicity Along the San Andreas Fault from "Lessons learned from the Loma Prieta, California, earthquake of October 17, 1989"

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.

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

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.

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 May 12, 2008, Great Sichuan Earthquake, also called the Wenchuan Earthquake, occurred at 14:28 local time, in Sichuan Province, China. The earthquake magnitudes were Mw = 7.9 (USGS), Ms = 8.0 (Chinese Earthquake Administration). The epicenter was 80 km west-northwest of Chengdu, the capital city of Sichuan province.

The May 12, 2008, Great Sichuan Earthquake, also called the Wenchuan Earthquake, occurred at 14:28 local time, in Sichuan Province, China. The earthquake magnitudes were Mw = 7.9 (USGS), Ms = 8.0 (Chinese Earthquake Administration). The epicenter was 80 km west-northwest of Chengdu, the capital city of Sichuan province.

The May 12, 2008, Great Sichuan Earthquake, also called the Wenchuan Earthquake, occurred at 14:28 local time, in Sichuan Province, China. The earthquake magnitudes were Mw = 7.9 (USGS), Ms = 8.0 (Chinese Earthquake Administration). The epicenter was 80 km west-northwest of Chengdu, the capital city of Sichuan province.

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.

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

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