Earthquake-Related Signals in Central Italy Detected by Hydrogeochemical and Satellite Techniques

Giovanni Martinelli,Lisa Pierotti,Mariano Lisi,Gianluca Facca,Valerio Tramutoli,Nicola Genzano,Fabrizio Gherardi

doi:10.3389/feart.2020.584716

Abstract

Central Apennines are one of the regions of highest seismic risk of Italy. A number of energetic events (M_W > 5) hit the region during the period 2004-2017, killing several hundreds of people (e.g., 294 casualties associated with the August 24th, 2016, M_W 6.0 event of Amatrice). These earthquakes impacted piezometric levels, springs discharge, and groundwater chemistry on a large area, even at distances of several tens of kilometers from the epicenters. Here we present a multidisciplinary dataset based on hydrogeochemical and satellite observations associated with the seismic events occurred in Central Italy during the period 2004-2017, that combines information derived from the application of groundwater monitoring and satellite techniques. Groundwater monitoring techniques allowed to detect hydrogeochemical anomalies in spring and well waters (20 sampling points over the observation period), whereas satellite techniques were applied to detect time-space variations in ground thermal emissions. We detected two significant, almost synchronous, anomalies in 2009 and 2016-2017 with both techniques, and we tentatively correlated them to crustal deformation processes. Part of the observed signals was detected before mainshocks, and they appear to be related to aseismic slip or to seismic slip eventually induced by minor fluctuations in seismicity. We argued that the combination of two factors, i.e., the shallow depth of local earthquakes and the concurrent deepening of groundwater circulation paths to several km depth, allowed for the recording of variations in the stress field by geofluids released at the surface.

Highlights

Central Italy is affected by intense crustal deformation processes driven by the relative motion of the African and the Eurasian plates
We propose a novel approach that combines groundwater monitoring and satellite techniques to indirectly evaluate variations in the stress field, and possibly examine the effects due to the crustal deformation processes associated with such variations
Geochemical effects of crustal deformation processes on geofluids in Central Italy have been evidenced by ground and satellite techniques

Summary

Introduction

Central Italy is affected by intense crustal deformation processes driven by the relative motion of the African and the Eurasian plates In this region, active extension occurs along the axial and western zones of the Apennine mountainous belt (backarc extension area, characterized by crustal thinning and active volcanism toward the Tyrrhenian Sea). Martinelli and Dadomo (2018) recently evidenced that a large part of possible geochemical precursory phenomena recorded worldwide have been found in areas characterized by i) shallow seismicity, ii) relatively high heat flux, and iii) significant crustal deformation rates. All these features are characteristics of the study area (e.g., Chiodini et al, 2004; Chiodini et al, 2011; Chiodini et al, 2020)

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