Abstract
Chemical and physical responses of groundwater to seismicity have been documented for thousands of years. Among the waves produced by earthquakes, Rayleigh waves can spread to great distances and produce hydrogeological perturbations in response to their passage. In this work, the groundwater level, which was continuously recorded in a monitoring well in Central Italy between July 2014 and December 2019, exhibited evident responses to dynamic crustal stress. In detail, 18 sharp variations of the groundwater level due to worldwide Mw ≥ 6.5 earthquakes were observed. Apart from earthquakes that occurred in Papua New Guinea and those with a hypocentral depth > 150 km, all far away Mw ≥ 7.6 earthquakes produced impulsive oscillations of groundwater. As the earthquake magnitude decreased, only some earthquakes with 6.5 ≤ Mw < 7.6 caused groundwater level perturbations, depending on the data acquisition frequency and epicentral distance from the monitoring well. A clear correlation between earthquake distance and magnitude in hydrogeological responses was found. Our results shed light on the hydrosensitivity of the study site and on the characteristics of fractured aquifer systems. Detecting the water table variations induced by distant earthquakes is another step towards a correct identification of (preseismic) hydrogeological changes due to near-field seismicity.
Highlights
Earthquakes are among the main natural processes that can cause the strongest perturbations in the Earth’s crust
November 2014 for PF60.2) the probe in the PF60.3 well recorded significant changes in groundwater level following the occurrence of many high magnitude earthquakes around the world (Mw ≥ 6.5)
Detailed analyses of groundwater level data corresponding to all 218 seismic events were processed, and 18 characteristic groundwater level behaviours were found and are shown in Fig. 3 together with the seismic trace of the vertical component recorded by two nearby seismometers
Summary
Earthquakes are among the main natural processes that can cause the strongest perturbations in the Earth’s crust. We present the results of the water level monitoring with a view to expanding the understanding of perturbations of fluids in the upper crust due to earthquakes, with a focus on groundwater–earthquake physical relationships Since these or similar probes are used by us and other geoscientists to identify potential hydrogeochemical precursors to nearby e arthquakes[2,5,9,20,33,34], identifying and filtering the effect on (and the cause of) the groundwater level induced by distant earthquakes is a pre-requisite to understanding the possible effect induced by the seismic cycle of nearby faults. Groundwater flow feeds base-flow springs in the gorges of the Pescara R iver9 [references therein]
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