Where do earthquakes most often occur?

Where do earthquakes most often occur?

Tom Jordan (Director, Southern California Earthquake Center (SCEC)) gives expert video advice on: What is the probability of a severe earthquake striking a major city?; Where do earthquakes most often occur?; What are the most common earthquake myths? and more...

Earthquakes most often occur on the boundaries between major tectonic plates. The earth's surface is broken into a dozen or so major plates, plus a number of smaller plates and those plates are moving with respect to each other. On the boundaries between two plates is where that motion occurs and that's where we find the big earthquakes. For example, in California there is a major plate boundary between the pacific plate to the west and the North American plate to the east. The fault that marks that boundary is the San Andreas fault and that's where we have some of the largest earthquakes in the continental United States.