Earthquake Geology: methods and applications

Earthquakes are complex natural phenomena that can be studied from different perspectives and using a variety of methods. Prior to the 20th century, the study of earthquakes (literally Seismology) was done by geologists, but when the seismograph was invented, field geologists were progressively set aside and the investigation of seismic events became an exclusive matter of seismologists, which conversely mainly focused on the seismic waves and the physics of the source, generally omitting to investigate the geological aspects of the fault, which in reality is the causative structure of most earthquakes. Only during the second half of the 20th century, became clear that the exploitation of geological data and the use of geological methodologies in their broadest sense are crucial for investigating seismic events and in general the active tectonics of an area. Indeed, structural, stratigraphic, geomorphological and remote sensing techniques and methods, among others, represent the modern tools in Earthquake Geology researches. The major advantages of Earthquake Geology is to examine a larger time window than instrumental, historical and archaeoseismological studies can do. Not secondarily, Earthquake Geology is also capable of detecting and examining the cumulative effects of earthquakes occurred in an area over very long periods. Indeed, linear and areal morphogenic earthquakes leave on the earth's surface permanent features that contribute to shape the landscape. Accordingly, geological investigations can detect, measure and study such features even several years, centuries or millennia after they were formed by earthquakes. Additionally, with geological studies, crucial information can be obtained for regions where instrumental seismic records or detailed historical seismological information are not available, but where destructive earthquakes hhave been generated in the past and similar events may be generated in the future. Geological approaches to the investigation of past earthquakes are fundamental to contribute in determining or inferring important parameters for SHA analyses, including the mean slip-rate, the maximum expected magnitude and the return period for a given magnitude.