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Earthquake, any sudden shaking of the ground caused by the passage of seismic waves through Earth’s rocks. Earthquakes occur most often along geologic faults, narrow zones where rock masses move in relation to one another.
Earthquake magnitude is a measure of the “size,” or amplitude, of the seismic waves generated by an earthquake source and recorded by seismographs. (The types and nature of these waves are described in the section Seismic waves .)
Japan earthquake and tsunami, severe natural disaster that occurred in northeastern Japan on March 11, 2011, and killed at least 20,000 people. A powerful earthquake off the coast of Honshu also generated a series of large tsunami waves that devastated many coastal areas and triggered a major nuclear accident.
Why is an earthquake dangerous? What are earthquake waves? How is earthquake magnitude measured? Where do earthquakes occur?
Richter scale (M L), quantitative measure of an earthquake’s magnitude (size), devised in 1935 by American seismologists Charles F. Richter and Beno Gutenberg. The earthquake’s magnitude is determined using the logarithm of the amplitude (height) of the largest seismic wave calibrated to a scale by a seismograph. Although modern scientific ...
Earthquakes—that is, sudden episodes of shaking ground—are caused by seismic waves (which result from the energy released by the breaking and slippage of one set of rocks against another). Aftershock is the term used to describe a shaking event that follows an earthquake.
Seismic wave, vibration generated by an earthquake, explosion, or similar energetic source and propagated within the Earth or along its surface. Earthquakes generate four principal types of elastic waves; two, known as body waves, travel within the Earth, whereas the other two, called surface.
Why is an earthquake dangerous? What are earthquake waves? How is earthquake magnitude measured? Where do earthquakes occur?
2010 Haiti earthquake, magnitude 7.0 earthquake that struck some 15 miles (25 km) southwest of the Haitian capital of Port-au-Prince on January 12, 2010. Haiti’s government estimated that more than 300,000 were killed, but other estimates were considerably smaller.
In an earthquake, huge masses of rock move beneath Earth’s surface and cause the ground to shake. Earthquakes occur constantly around the world. Often they are too small for people to feel at all, but some earthquakes are massive. They can cause great destruction.