# Plot the earthquakes on the map Where do Earthquakes occur?

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Plot the earthquakes on the map Where do Earthquakes occur?

EW WE N S

An earthquake is any sudden movement of the Earths Crust

Stress is: A force per unit area A force acting on rock to change the shape or volume Graph courtesy of: http://geology.csupomona.edu/dwtarman/alert%20files/structural%20topics/stress.htm

* 3 Types: Result of 2 opposite forces Result of at least 2 opposite forces; may be as many as 4 forces Result of 2 opposite forces

Plastic Deformation Results in folded rock but not earthquakes Elastic Deformation Leads to Earthquakes

* A bend in rock * Does NOT result in earthquakes * Occurs when rock is in plastic state

* Anticline: convex (upward) fold * Syncline: concave (downward) fold Diagrams courtesy of:: http://www.glossary.oilfield.slb.com/Display.cfm?Term=syncline

A SURFACE ALONG WHICH ROCKS BREAK AND SLIDE PAST EACH OTHER * RESULTS IN AN EARTHQUAKE Photos courtesy of: http://pubs.usgs.gov/gip/earthq1/how.html

Once that happens the rock breaks (faults), movement occurs along the fault and energy is released (earthquake). Rocks under pressure will continue to bend and deform until their elastic limit is reached.

Photo courtesy of: http://www.thetech.org/exhibits/online/quakes/faults/cycles1.html

Pressure Changes Excessive Sediment Layers-crack plates Plates undergo vertical movement above bumps in the mantle

Most earthquakes occur at plate boundaries. Transform boundaries experience the most quakes

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