Copyright Information: All images are in the public domain and available for free. If you use this image, credit NOAA/NGDC, University of Colorado. |
The Imperial fault east of El Centro, California, shows characteristic right stepping en echelon fractures. The rupture on the fault during the magnitude 6.9 earthquake of October 15, 1979, in Imperial Valley, California, extended from about 4 km north of the international border to about 4 km south of Brawley. Maximum lateral displacement was about 55 cm in the Heber dunes, and maximum vertical displacement was 19 cm southeast of Brawley. The earthquake injured 19 people, and damaged more than 2,000 homes and businesses in the Imperial Valley. Property damage was estimated at $30 million. Image Credit: University of Colorado Through the study of faults and their effects, much can be learned about the size and recurrence intervals of earthquakes. Faults also teach us about crustal movements that have produced mountains and changed continents. Initially a section of Earth's crust may merely bend under pressure to a new position. Or slow movement known as seismic creep may continue unhindered along a fault plane. However stresses often continue to build until they exceed the strength of the rock in that section of crust. The rock then breaks, and an earthquake occurs, sometimes releasing massive amounts of energy. The ensuing earth displacement is known as a fault. This slide set describes the mechanism and types of faulting. It illustrates a variety of fault expressions in natural and manmade features. |
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