Earthquakes Indicator Explain how earthquakes result from forces inside Earth.

Why should we study earthquakes?

Assessing Prior Knowledge What have you heard about earthquakes lately?

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Earthquakes Earthquakes are a result of motion within the earth. This only occurs where the earth is solid and therefore can only occur within about 100 miles of the surface

Indirect Evidence Earthquakes provide the best INDIRECT evidence for inferences regarding the interior structure of the earth.

Inference Forces inside the Earth cause certain effects as rocks break and seismic waves of energy spread out from the focus of the earthquake. –Cause: forces inside earth create change –Effect: rocks break, seismic waves of energy spread out from earthquake focus

Earthquakes

What Causes Earthquakes? Forces/stresses (compression, shearing, tension) along faults (normal, reverse, strike-slip) can build up as blocks of rock move

Effects of Earthquakes If the pressure becomes too great, the rock breaks at a weak point along the fault, and energy is released. This energy spreads outward in all directions as vibrations called seismic waves.

What plate boundaries are involved in earthquakes? Convergent Oceanic- Continental Boundary

What plate boundaries are involved in earthquakes? Transform Boundary

BoundaryForceFaultEffectEarthquake Example Convergent Oceanic- Continental Compression OC   CC ReverseEarthquake! (and volcanoes, mountain building) Japan TransformShearing CC   CC Strike-SlipEarthquake!San Andreas Fault, CA

Earthquakes

What is the focus of an earthquake? Point in the crust, or mantle, where energy is released.

What is the epicenter of an earthquake? Point on Earth’s surface directly above the focus The energy is greatest when it reaches the surface at the epicenter.

Earthquakes

Tsunami/Tidal Waves Tidal waves or Tsunamis result when a large section of the sea floor suddenly moves and therefore displaces a massive amount of water.

Tidal waves or Tsunamis result when the low amplitude long wavelength waves reach the shallow shoreline and begin to feel the bottom of the sea floor. This Shortens the wavelength and increase the amplitude (height).

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Earthquakes Location of worldwide earthquakes

Earthquakes Earthquakes by depth. Notice that the deep earthquakes occur only at subduction zones.

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