The Hydrological Impact of Historical and Modern Earthquakes in Central-Southern Italy: Data Analysis and Seismotectonic Insights

Abstract We present the results of research conducted on the hydrological effects induced by historical and modern earthquakes in the central-southern Apennines of Italy. We investigated thirty-nine seismic events of magnitude between M 4.1 and 7.1 that occurred between 1688 and 2020. We collected 526 observations of coseismic and postseismic hydrological effects such as increase or decrease in streamflow, variations in the water levels in wells, formation and/or disappearance of springs and changes in their discharge, and changes in the chemical and physical characteristics of waters. More than half of the observations were new data unpublished to date in the scientific literature. We find that the ease of finding data of interest is strongly influenced by the historical period in which the seismic event occurred. We summarize the methodology of data retrieval and its classification and present examples and maps of coseismic hydrological changes associated with individual seismic events. Most of our novel data derive from seismic postcards, macroseismic questionnaires, and hydrographic annals. However, a nonnegligible set of data comes from a careful rereading of sources—both historical and modern—that were at first considered fruitless. The majority of data concerns an excess flow in streams and springs, and physical–chemical variations such as turbidity, an increase in temperature, and gas emission. We also find that the maximum distance to which seismically induced streamflow responses have been reported can be related to the earthquake magnitude and use this distance to derive an alternative magnitude for some of the strongest earthquakes of our dataset. Finally, we show a potential application of this type of research because the distribution of coseismic hydrological changes can provide constraints in discriminating between the causative faults of strong historical seismic events for which the instrumental data are scarce or not available.