It seeks to understand which faults are responsible for seismic activity in an area by analysing a combination of regional tectonics, recent instrumentally recorded events, accounts of historical earthquakes and geomorphological evidence.
In order to understand the seismic hazard of an area it is necessary not only to know where potentially active faults are, but also the orientation of the stress field.
[3] As focal mechanisms give two potential active fault plane orientations, other evidence is required to interpret the origin of an individual event.
However, such data is needed to fill the gaps in the instrumental record, particularly in areas with either relatively low seismicity or where the repeat periods for major earthquakes is more than a hundred years.
In some cases such observations can be used quantitatively to constrain the repeat period of major earthquakes, such as the raised beaches of Turakirae Head recording the history of coseismic uplift of the Rimutaka Range due to displacement on the Wairarapa Fault in North Island, New Zealand.