​An earthquake can be caused by the sudden shifting of rock plates beneath the earth’s surface or from the pressure of rising magma in volcanic areas. They usually occur along fault lines (where the rock plates that form the earth’s crust meet), or in volcanic areas. The shaking may be very slight, or it may be quite violent. Loud rumblings often accompany earthquakes, along with significant structural damage, power outages, explosions, or fires.

 

Intraplate quakes occur far from plate edges and happen when stress builds up and the Earth's crust is stretched or squeezed together until it rips. There are several different types of faults. These faults can stretch in length from a few inches to many hundreds of miles long. They can be horizontal, vertical, or at an angle.

 

Earthquake waves are measured on sensitive instruments called seismographs. The Richter scale assigns quakes a number based on the power of its seismic waves. Thousands of quakes occur every day around the globe, most of them too weak to be felt. Every year about 10,000 people, on average, die as a result of earthquakes.