Sandpiles and earthquakes

Abstract

This aerial photo of the San Andreas Fault is impressive (Fig. 1). The fault extends itself over roughly 1,300 km through California in the United States. It follows the boundary between the Pacific Plate and the North American Plate. The two tectonic plates move against each other (only few centimeters per year) slowly but firmly. Their motion affects rocks of the earth crust and deforms them elastically. Eventually, elastic stress gets so high that it exceeds rock strength, causes fractures and releases most of the accumulated energy.