Earthquakes are expressions of ongoing tectonic processes that are caused by sudden releases of pressure. They can be classified by location, either as intraplate disturbances on faults like the Rhine Rift Valley, or as interplate earthquakes, where two tectonic plates meet and subduct, or by depth, as shallow-focus or deep-focus quakes. Most damage is done by relatively weak but shallow earthquakes. Along faults, visible slippages of several meters can occur.