An earthquake is defined as a series of vibrations within the earth's crust that are caused by the rupture of its rocks. This rupture is due to the gradual accumulation of elastic strain within the crust.
There are several causes for earthquakes, including sudden events such as volcanic eruptions. The most powerful earthquakes are caused by dislocations in the crust. Earthquakes often occur around faults, which are slippages between blocks on the earth's crust. Even after an earthquake has occurred along a fault line, another may occur if some stress remains in the crust.
There are several key points to an earthquake. The focal depth refers to the depth beneath the surface of the earthquake's energy origination. This point of origination is called the focus. The point on the earth's surface located directly above the focus is the earthquake's epicenter.
In addition to the immediate damage, secondary damage may be caused by the natural disasters spawned as a result of the earthquake. These disasters include landslides and tsunamis, which are often more destructive than the earthquake itself.
Earthquakes are typically measured using the Richter scale, which rates them from one to 10. This scale is logarithmic; each whole number indicates a tenfold increase.