Earthquakes

Earthquakes are a shaking of the surface which can be strong enough to destroy buildings and kill many people. Earthquakes release energy suddenly from the Earth’s crust, causing seismic waves which propagate away from the source and all around the Earth.

The epicenter of an earthquake is the location where the energy is re- leased. Earthquakes are usually caused by a rupture of a fault. If the epi- center of an earthquake is located below the ocean, this can also trigger tsunamis. Another deadly force where a giant wave is created which will flood nearby land and drag things back out to see. If the epicenter is located on land, this can also trigger landslides which can cause a lot of death and destruction.

Figure 1: Three types of faults causing earthquakes

There are three main types of fault which can cause earthquakes: normal, reverse (thrust) and strike-slip. Figure 1 shows the types of faults that can cause earthquakes.

Figures 2 and 3 show the location of large earthquakes over the past few decades. Figure 2 also shows the location of major cities with a population of a million people or more, to get an idea of devastating an earthquake can be in a given location. Figure 3 shows the depth of the earthquakes (given by color coding them). The more shallow an earthquake, the more damage and destruction it will do at the surface.

Figure 2: Location of large earthquakes since 1973 and major cities on Earth

This figure from Cornell University

Source: Princeton University