Earthquake are caused by faults which may be on surface (Epicenter) or subsurface (focus Hypocenter). Does a fault break all at once? Oblique view of a right-lateral strike-slip fault with multiple asperities. When one asperity slips, there is an added load on the adjoining asperities. In a large earthquake there is a cascading effect as each zone that slips loads the next zone, which then slips, and so forth, sometime for hundreds of miles, in a process that can continue for 5 or more minutes. An asperity is an area on a fault that is stuck or locked. Scientists study areas along long fault zones that have not had earthquakes in a long time in order to determine where the next earthquake may occur; as long faults move, all areas of it will, at some point, become "unstuck" causing an earthquake relative to the the size of the asperity that finally breaks. Objectives: An asperity is an area on a fault that is stuck or locked. An area along an active fault that has not had an earthquake in a long time might be vulnerable to a large earthquake. In a large earthquake there is a cascading effect as each zone that slips loads the next zone. The earthquake rupture often begins at an asperity Keypoints: An asperity is an area on a fault that is stuck or locked. An area along an active fault that has not had an earthquake in a long time might be vulnerable to a large earthquake. In a large earthquake there is a cascading effect as each zone that slips loads the next zone. The earthquake rupture often begins at an asperity