Point of fracture or slippage, termed Focus or Hypocenter
- Define some earthquake terms
- Magnitude: The magnitude of an earthquake is frequently given as a number on the Richter scale. This scale measures the amplitude of ground motion.
- Local ground motion from the earthquake will depend on the distance from the fault source to the building and the surface geology between the point of rupture and the building.
- Earth scientists use certain terms to define seismic distances. See figure.
- Focus, or hypocenter: The point at which the slippage occurs
- In general, the shorter the distance from this point of rupture to the building, the higher the vibratory ground motions from earthquake forces.
- Focal depth: Distance from hypocenter to surface of the earth
- Epicenter ("epi" being Greek for "above"). Point directly above the hypocenter. The locations of earthquakes are frequently identified by the geographic location of their epicenter.