 Complete the following phrase:  This is so because the energy released in an earthquake, and thus its magnitude, is proportional to the area of the fault that ruptures and the stress drop. Therefore, the longer the length and the wider the width of the faulted area, the larger the resulting magnitude. The topmost, brittle part of the Earths crust, and the cool slabs of the tectonic plates that are descending down into the hot mantle, are the only parts of our planet that can store elastic energy and release it in fault ruptures. Rocks hotter than about flow in response to stress; they do not rupture in earthquakes. The maximum observed lengths of ruptures and mapped faults which may break in a single rupture are approximately . Examples are the earthquakes in Alaska 1957, Chile 1960, and Sumatra 2004, all in subduction zones. The longest earthquake ruptures on strike-slip faults, like the San Andreas Fault 1857, 1906, the North Anatolian Fault in Turkey 