The epicenter is the point on a planet’s surface that is directly above the hypocenter, which is also called the focus of an earthquake. The hypocenter is the starting point of fracturing rocks, and it is the actual point where earthquakes begin.
Hypocenters are found at a considerable depth below the surface. Vibrating waves move away from the hypocenter in various directions. The waves can travel to all places on the Earth and make the planet rapidly vibrate because of their immense power.
While the hypocenter is the origin of earthquakes, scientists typically plot the epicenter on a map to identify the location of the quake. This method of mapping an earthquake’s location is the reason large quakes are usually named after the city or geographic location closest to the epicenter.
Shallow-focus earthquakes occur from 0 to 40 miles deep. They result from the movement of crustal plates against each other, and they are measured using the Richter scale. Deep-focus earthquakes occur more than 180 miles below the surface of the Earth. They are common in island arcs and deep ocean trenches where plates slip over each other in subduction zones. Deep-focus earthquakes are measured using the moment magnitude scale. Shallow-focus earthquakes occur more frequently and are more destructive than deep-focus earthquakes.