Hydroseismograms at Gran Sasso aquifer, central Italy, for earthquake hydrology studies

The use of hydroseimograms (i.e., high frequency pore pressure monitoring in wells in rock) emerges as a promising tool for a better understanding of the physics underlying earthquakes, as well as for seismic activity monitoring and/or prediction. This study investigates the earthquake detection capability of a hydraulic pressure device (HPD) installed in the Gran Sasso aquifer (GSA), Italy. The HPD, located in boreholes S13 and S14, near the INGV seismic station, GIGS, monitors hydraulic pressure changes within the aquifer. We compared data from the HPD and from GIGS to assess the HPD's ability to detect earthquakes. The analysis covered the period from May 2015 to December 2023. The HPD successfully identified 148 out of 1068 analyzed earthquakes. Compared to previous studies, our HPD displayed significantly higher sensitivity, particularly for crustal earthquakes. These HPD devices show distinctive features, such as deep location, high frequency sampling (20 Hz), and hosting wells intercepting the main fault network. The unique location of the HPD, combined with its sensitivity to seismic events, makes it a valuable tool for continuous monitoring of earthquake activity, coupled with pore pressure trends and anomalies, in the region. These results confirm the potential of the HPD system for earthquake detection within the GSA. Future studies will continue to evaluate the HPD's capabilities and its role in earthquake hazard assessment, as well as its potential use in other areas worldwide.