What is an Earthquake? Pgs. 218 - 221 Chapter 8.1 What is an Earthquake? Pgs. 218 - 221

An earthquake is the vibration of Earth produced by the rapid release of energy. Usually these are caused by slips along a break in the Earth’s crust. Earthquakes

Focus and Epicenter Focus – where an earthquake starts When the energy is released when an earthquake starts it moves in all directions from the focus. The place on the surface where an earthquake occurs is the epicenter. This is the area on the surface right above the focus. Focus and Epicenter

Earthquakes are caused along faults Earthquakes are caused along faults. These are fractures in Earth where movement has occurred. Faults

Rocks will bend, and in that bend is stored energy Rocks will bend, and in that bend is stored energy. Once the rock moves, or slips, it releases that energy. The slipping of the rock is the earthquake. Cause of Earthquakes

Elastic Rebound Hypothesis Most earthquakes are produced by the rapid release of elastic energy stored in rock that has had great forces act on it. When the strength of the rock is too much, it suddenly breaks, causing an earthquake. Elastic Rebound Hypothesis

Aftershocks and Foreshocks Aftershocks are not as strong as the main earthquake but they will happen after a major earthquake. Foreshocks will occur before a major earthquake. Aftershocks and Foreshocks