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A force that acts on rock to change its shape or volume.


the action of stretching something tight


stress that squeezes rock until it folds or breaks


Stress that pushes masses of rock in opposite directions, in a sideways movement.

normal fault

an inclined fault in which the hanging wall appears to have slipped downward relative to the footwall

hanging wall

the upper wall of an inclined fault

foot wall

The block of rock that forms the lower half of a fault

reverse fault

a geological fault in which the upper side appears to have been pushed upward by compression

strike-slip fault

a type of fault where rocks on either side move past each other sideways with little up or down motion


a fold in rock that bends upward into an arch


a fold in rock that bends downward to form a valley


a large area of flat land elevated high above sea level


the shaking that results from the movement of rock beneath Earth's surface


The point beneath Earth's surface where rock breaks under stress and causes an earthquake


the point on the Earth's surface directly above the focus of an earthquake

P waves

A type of seismic wave that compresses and expands the ground

S waves

A type of seismic wave that moves the ground up and down or side to side

surface waves

are the slowest and largest of the seismic waves and cause most of the destruction during an earthquake

mercalli scale

a scale that rates earthquakes according to their intensity and how much damage they cause at a particular place


The measurement of an Earthquake's strength based on seismic waves and movement along faults.

richter scale

a scale that rates an earthquake's magnitude based on the size of its seismic waves


an instrument that records earthquake waves

moment magnitude scale

a scale that rates earthquakes by estimating the total energy released by an earthquake


the record of an earthquake's seismic waves produced by a seismograph


the force that opposes the motion of one surface as it moves across another surface


The process by which an earthquake's violent movement suddenly turns loose soil into liquid mud


an earthquake that occurs after a larger earthquake in the same area


a giant wave caused by an earthquake on the ocean floor

base-isolated building

A building mounted on bearings designed to absorb the energy of an earthquake.

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