What is an earthquake?
An earthquake is caused by a sudden slipping or movement of a portion of the earth’s outer layer, called the crust. This sudden movement occurs along faults, or breaks in the earth’s crust along which blocks of earth move when built-up strain is released. The release of tension can cause the ground to shake violently, resulting in damage to buildings, roads, and utility systems over a wide area. Earthquakes can occur at anytime of the day or year with no warning.