A sudden slipping or movement of a portion of the Earth's crust, accompanied and followed by a series of vibrations.

A building that is earthquake proof is expected to retain enough structural integrity to be safely re-used after the event. High value or essential facilities (fire and police stations, EOCs, or health facilities, which are all critical in the aftermath of a devastating earthquake, and schools) may have to be built to a higher standard than required by the code to remain operational after an event.

A building that is earthquake resistant is expected to retain sufficient structural integrity during an earthquake to protect the people using the facility and permit them to evacuate safely after the event. New structures, if built to code are (by definition) earthquake resistant but not earthquake proof.

The place on the earth's surface directly above the point on the fault where the earthquake rupture began. Once fault slippage begins, it expands along the fault during the earthquake and can extend hundreds of metres before stopping.