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Quaking, Shaking, Earth. All about Earthquakes. What is an earthquake?. Simply put: An earthquake is the shaking of the earth. Shaking or trembling caused by a sudden release of elastic energy Usually associated with faulting or breaking of rocks.
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Quaking, Shaking, Earth All about Earthquakes
What is an earthquake? • Simply put: • An earthquake is the shaking of the earth. • Shaking or trembling caused by a sudden release of elastic energy • Usually associated with faulting or breaking of rocks
Many buildings in Charleston, South Carolina, were damaged or destroyed by the large earthquake that occurred August 31, 1886. Picture from the United States Geological Service www.usgs.gov
San Francisco, California, Earthquake April 18, 1906. East side of Howard Street near Seventeenth Street. All houses shifted toward the left. The tall house dropped from its south foundation wall and leaned against its neighbor. 1906. Picture from USGS.GOV
San Fernando, California, Earthquake February 1971. Collapsed overpass connecting Foothill Boulevard and the Golden State Freeway. Feb 10, 1971. Photo by R.E. Wallace, USGS. www.usgs.gov Free powerpoint template: www.brainybetty.com
What causes an earthquake? • Earthquakes are the Earth's natural means of releasing stress. • Due to the constant motion of the Earth’ plates, this put stress on the edges of the plates. • To relieve this stress, the rocks tend to bend, compress, or stretch. An aerial view of the San Andreas fault in the Carrizo Plain, Central California. Picture from www.usgs.gov
Elastic Rebound • Explains how energy is stored in Rocks. • Rupture occurs and the rocks quickly rebound to an undeformed shape • Energy is released in waves that radiate outward from the fault Free powerpoint template: www.brainybetty.com
Locatin' the Shakin' • Focus: the place on the Earth’s crust where the pressure was released. • Epicenter: the spot on the Earth’s surface directly above the focus.
Faults • If the force is great enough, the rocks will break. • An earthquake is the vibrations produced by the breaking of rock. • Most earthquakes occur near plate boundaries. The Hanshin expressway in Kobe, Japan collapsed due to an earthquake in 1995. Picture from http://www.ce.washington.edu/~liquefaction/html/quakes/kobe/kobe.html
Normal Fault • Rock above the fault surface moves downward in relation to rock below the fault surface. • Plate Motion is? • Divergent
Reverse Fault • Reverse faults result from compression forces that squeeze rock. • What kind of plate motion is this? • Convergent
Strike-slip Fault • At a strike-slip fault, rocks on either side of the fault are moving past each other without much upward or downward movement. • Plate Motion is… • Transform • http://www.iris.edu/gifs/animations/faults.htm