Some of the largest earthquakes ever recorded include the Chilean earthquake of 1960, the Prince William Sound earthquake of 1964 and the earthquake in Sumatra, Indonesia, in 2004. Other large earthquakes occurred in Sendai, Japan, in 2011 and Kamchatka, Russia, in 1952. While even larger earthquakes may have occurred in the past, the technology did not yet exist for accurate measurements and records.
Earthquakes are the result of a sudden release of pressure within the Earth's crust, which causes a perceptible shaking of its surface. Powerful earthquakes are violent enough to damage or destroy major buildings and often result in thousands of casualties. Scientific instruments known as seismometers detect the seismic waves of earthquakes, providing the data needed to measure their relative strength. Scientists use the moment magnitude and Richter magnitude scales to measure the strength of earthquakes.
Earthquakes manifest themselves by violently shaking or displacing the ground. Earthquake epicenters that occur offshore may shift the seafloor, producing tsunamis. The term "earthquake" describes any natural or man-made event that produces seismic waves. While landslides, nuclear testing and mine blasts are capable of producing earthquakes, only the rupture of a geologic fault line or volcanic event produces sufficient force to create the largest earthquakes.