Editing Epicenter (section)

==Fault rupture==
{{Main|Earthquake rupture}}
The point at which fault slipping begins is referred to as the focus of the earthquake.<ref name="JordanGrotzinger2012"/> The fault rupture begins at the focus and then expands along the fault surface. The rupture stops where the stresses become insufficient to continue breaking the fault (because the rocks are stronger) or where the rupture enters ductile material.<ref name="JordanGrotzinger2012"/> The magnitude of an earthquake is related to the total area of its fault rupture.<ref name="JordanGrotzinger2012"/> Most earthquakes are small, with rupture dimensions less than the depth of the focus so the rupture doesn't break the surface, but in high magnitude, destructive earthquakes, surface breaks are common.<ref name="JordanGrotzinger2012"/> Fault ruptures in large earthquakes can extend for more than {{cvt|100|km|||}}.<ref name="JordanGrotzinger2012"/> When a fault ruptures unilaterally (with the epicenter at or near the end of the fault break) the waves are stronger in one direction along the fault.<ref>{{Cite web|url=https://earthquake.usgs.gov/data/rupture/directivity.php|title=What is Directivity?|publisher=United States Geological Survey|access-date=2018-07-01}}</ref>