Reappraisal of Data of Hydrological Changes Associated with Some Strong Historical Italian Earthquakes

Historical seismology retrieves information about the effects of earthquakes that occurred
in the past, mostly regarding the damage, but also on environmental effects. In this paper, we describe
the methodology of our research on earthquake-induced hydrological effects, which have been long
observed and documented, and are among the most outstanding coseismic phenomena. The method
of research follows two distinct paths, depending on whether the investigated event occurred before
or after the end of the 18th Century. For the most ancient events, we present examples of historical
accounts, local reports, private letters, and diaries, in which the information of interest is often
hidden within broader descriptions and mentioned as a minor curiosity. On the contrary, for more
recent earthquakes, the research benefits from the growing interest in naturalistic observations that
marked the onset of the 19th Century, and is achieved through detailed descriptions, journals, seismic
postcards, and through the first systematic collections of instrumental data. Finally, we describe
a possible method of classification of the hydrological data and show an analysis of the potential
applications and outcomes of this type of research.