What is the relationship between Quaternary faults and earthquakes?
Earthquakes occur as a result of slip on faults in the Earths crust. If the earthquake forms (nucleates) deep in the crust or has a magnitude below about 6, the slip on the fault may be unable to reach the surface. Those earthquakes that occur at shallower depths or have greater magnitudes commonly form a rupture at the surface or cause other types of deformation, such as liquefaction features. It is these features that are the subject of our Quaternary fault and fold database. The relationship between earthquakes and Quaternary faults is similar to the relationship between earthquakes and older faults except that Quaternary faults are those that have been recognized at the surface and which have moved in the past 1,600,000 years, the duration of the Quaternary epoch.