An earthquake is a trembling or a shaking movement of the Earth's surface. Earthquakes typically result from the movement of faults, quasi-planar zones of deformation within its uppermost layers. The word earthquake is also widely used to indicate the source region itself. The solid earth is in slow but constant motion and earthquakes occur where the resulting stress exceeds the capacity of Earth materials to support it.
Earthquakes occur every day on Earth, but the majority of them are minor and cause no damage those less than 5 on ritcher scale. Large earthquakes can cause serious destruction and massive loss of life through a variety of agents of damage, including fault rupture, vibratory ground motion (i.e., shaking), inundation, various kinds of permanent ground failure and fire or a release of hazardous materials. In a particular earthquake, any of these agents of damage can dominate, and historically each has caused major damage and great loss of life, but for most of the earthquakes shaking is the dominant and most widespread cause of damage.
Damage from the 1906 San Francisco earthquake
Where do most earthquakes occur?
The earth is made of layers, divided into the crust, mantle, and core. The crust is the Earth’s surface, a thin, hard layer of rock, broken into many pieces. Some form continents, others the ocean floor, but they are always moving. According to the theory of plate tectonics, the earth’s crust is made of six major plates and nine smaller ones that lie on the mantle, a thicker, denser layer of hot, soft, molten rock. These plates float around within the mantle, in a hot, soft zone known as the asthenosphere.
The core is made up of even hotter rocks below the mantle, and currents of burning rock rise up through the mantle. These currents spread.......
