The point of first break or movement along a fault is called the earthquake's focus . The point on the earth's surface directly above the focus is called the epicenter . There are several types of earthquake, or seismic, waves. P-waves are compressional waves and can travel through the earth's liquid outer core. S-waves are shear waves and cannot travel through the earth's core.
Surface waves travel along the earth's surface and are the most destructive.
The magnitude of an earthquake is a measure of the amount of vertical displacement associated with the earthquake and is usually reported using the Richtor magnitude scale. The intensity of an earthquake is a measure of the damaging effects of an earthquake at a particular location and is usually reported on the Modified Mercall Scale. Ground motion is the primary hazard associated with earthquakes. Ground failures including landslides and liquifaction. Liquifaction is a quicksand condition arising in wet soil shaken by seismic waves.