The focus, or hypocentre, of an earthquake is its point of origin, where energy is first released
The epicentre is the point on Earth’s surface that is directly above the focus
Seismic, or shock, waves are produced by earthquakes and can be either longitudinal “primary waves” (P-waves) or transverse “secondary waves” (S-waves); secondary waves normally cause more damage
The Richter magnitude scale is a logarithmic scale that assigns a magnitude number to quantify the energy released by an earthquake
It has since been succeeded by the Moment magnitude scale
The Mercalli intensity scale assigns a magnitude to an earthquake according to its effects on the Earth’s surface, humans, objects of nature and man-made structures