The variation of stress acting on crustal rocks determines pressure gradients able to mobilize fluids. Fluid motions are the most rapid
response to the modification of the tectonic stress. Therefore, they may represent useful indicators of transient phenomena that may
evolve into an earthquake. Coseismic chemical, water table depth and spring supply variations have been widely described. Moreover, in several cases, these modifications were starting before the mainshock, hence representing potentially reliable seismic precursors. However, these variations differ as a function of the tectonic setting (i.e., extensional, contractional, strike-slip). In this research project we intend to monitor the depth, temperature, salinity variation in few water wells in Abruzzo and Molise, along areas with high seismic hazard. We expect to record signals of stress modification that may eventually evolve into an earthquake. The goal is to install a multiparametric (GPS, SAR, seismological and hydrogeochemical) prototype observatory able to alert for a possible imminent seismic event.
The topic is of paramount scientific and social importance because earthquakes determine the loss of human lives and heavy economic damages. In parallel to the necessary activities aimed at increasing the resilience of buildings, we must invest in understanding the mechanisms of seismic generation and to pursue researches in transients and seismic precursors that may precede strong earthquakes. Here we propose to integrate hydrogeochemical signals that may indicate a preparatory phase, integrating the geodetic and seismological data.
Therefore, the project aims to focus on the analysis of hydrogeochemical transients that may represent seismic precursors. The innovation relies on two main issues, 1) the analysis will consider the differences of fluid reaction to stress changes due to extensional versus contractional tectonic settings; in fact, the fluid movements are opposed in the two geological realms; 2) the monitoring will be associated to the contemporaneous analysis of possible foreshocks seismicity, strain rate variations detected by the GPS Italian network (RING) and the InSAR surveillance operated 24h/7d by the INGV. The advancement in the knowledge on the seismic precursors will be performed only considering the differences among the three main types of tectonic settings because the reaction of the fluid to stress changes is different as a function of dilation or contraction of crustal rocks. Moreover, the multiparametric study is fundamental in order to cross-check, validate, and separate hydrogeochemical transients from seasonal inputs.
The experience of the first experiment performed at Bussi, near Sulmona, has been extremely promising (Barberio et al. 2017, SREP). We expect to provide evidence of more robust seismic precursors increasing the network of monitoring sites. The water table and springs are the main targets and during the last two main sequences (L¿Aquila 2009 and Amatrice-Norcia 2016) have provided sudden volumetric (e.g., >100 millions of m3) and chemical increase of the hydrological parameters. The hydrogeological increase of water discharge increases as the monitoring site is closer to the seismic source (hypocenter). Therefore, the aim is to have a higher coverage of monitoring sites that may be statistically in the vicinity of the next earthquakes.