I also learned how to locate the epicenter of an earthquake by using a time-travel graph, and triangulation from three earthquake recording stations. These images were taken from USGS . An earthquake is caused by friction under the earth s crust. The point at which the earthquake occurs under the surface is called the focus. The point on the earth's surface at which the earthquake occurs is the epicenter.
Earthquakes commonly occur on fault lines.
When plate tectonic boundaries slip past each other, they release tension, and this movement can cause the earth to shake, thus producing what we know as an earthquake. There are two scales which earthquakes can be measured by. One type of scale is called the Richter Scale. The Richter Scale was developed by Charles F. Richter in 1935. The second type of scale is called the Mercalli Intensity scale.