shaking and vibration at the surface of the earth resulting from underground movement along a fault plane of from volcanic activity
An earthquake (also known as a quake, tremor, or temblor) is the result of a sudden release of energy in the Earth's crust that creates seismic waves. Earthquakes are recorded with a seismometer, also known as a seismograph. The moment magnitude (or the related and mostly obsolete Richter magnitude) of an earthquake is conventionally reported, with magnitude 3 or lower earthquakes being mostly imperceptible and magnitude 7 causing serious damage over large areas. Intensity of shaking is measured on the modified Mercalli scale.
Release of energy waves called seismic waves in the crust of earth, leads to the creation of a natural disaster called earthquake. Earthquakes can be recorded using an instrument called as seismometer.
An earthquake is a vibration of the Earth produced by a rapid release of energy (Tarbuck 378). The main features include the focus, the location within the Earth where the earthquake rupture starts, and the epicenter, the point on the Earth's surface directly above the focus. Earthquakes have a greater effect on society than most people think. These effects range from economical to structural to mental. An earthquake only occurs for a few brief moments; the aftershocks can continue for weeks; the damage can continue for years.
How It Comes ?
Earth has about 800 moderate earthquakes every year. Another 120 earthquakes occur each year in the strong range. About 18 major earthquakes come, and one great earthquake will take place each year. Since 1990 112,199 people have died in earthquakes throughout the world. Sixty-eight of these deaths were in the United States. The United States has around 3000 earthquakes each year. Although the majority of these are below the moderate range, approximately 10 earthquakes take place annually in the United States are in the destructive range.
Signs Of Earthquake ?
Thermal precursor: A few months before the occurrence of an earthquake the average temperature of the area keeps increasing. Weather report bulletins refer to temperatures above or below average by so many degrees. It is seen that in case the area is heading for an earthquake, the average temperature goes on increasing. On the day of the earthquake it is about 5 to 9 degrees Celsius above the average normal temperature for that day. This could be monitored by the meteorology department and also by thermometers inside homes.
Recent research indicates an increase in the intensity of electromagnetic waves just before certain seismic and volcanic activity. But uncertainties concerning these phenomena remain.
Post-seismic emissions may be easily explained due to acoustic waves generated during ground movements caused by the earthquake. However, pre-seismic signals observed in the upper atmosphere remain poorly understood.
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