Instrumentally Recorded Events
Since the early 20th century, sufficient information has been available from seismometers to allow the location, depth and magnitude of earthquakes to be calculated. In terms of identifying the fault responsible for an earthquake where there is no clear surface trace, recording the locations of aftershocks generally gives a strong indication of the strike of the fault.
In the last 30 years, it has been possible to routinely calculate focal mechanisms from teleseismic data. Catalogues of events with calculated focal mechanisms are now available online, such as the searchable catalogue from the NEIC. As focal mechanisms give two potential active fault plane orientations, other evidence is required to interpret the origin of an individual event. Although only available for a restricted time period, in areas of moderate to intense seismicity there is probably sufficient data to characterise the type of seismicity in an area, if not all the active structures.
Read more about this topic: Seismotectonics, Methodology, Earthquakes
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—Hannah Arendt (1906–1975)
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—Herman Melville (1819–1891)