The Role of Faults in Groundwater Circulation before and after Seismic Events: Insights from Tracers, Water Isotopes and Geochemistry

Abstract

The interaction between fluids and tectonic structures such as fault systems is a much-discussed issue. Many scientific works are aimed at understanding what the role of fault systems in the displacement of deep fluids is, by investigating the interaction between the upper mantle, the lower crustal portion and the upraising of gasses carried by liquids. Many other scientific works try to explore the interaction between the recharge processes, i.e., precipitation, and the fault zones, aiming to recognize the function of the abovementioned structures and their capability to direct groundwater flow towards preferential drainage areas. Understanding the role of faults in the recharge processes of punctual and linear springs, meant as gaining streams, is a key point in hydrogeology, as it is known that faults can act either as flow barriers or as preferential flow paths. In this work an investigation of a fault system located in the Nera River catchment (Italy), based on geo-structural investigations, tracer tests, geochemical and isotopic recharge modelling, allows to identify the role of the normal fault system before and after the 2016–2017 central Italy seismic sequence (Mmax = 6.5). The outcome was achieved by an integrated approach consisting of a structural geology field work, combined with GIS-based analysis, and of a hydrogeological investigation based on artificial tracer tests and geochemical and isotopic analyses.

A Holistic Approach to Study Groundwater-Surface Water Modifications Induced by Strong Earthquakes: The Case of Campiano Catchment (Central Italy)

“…is composed of stratified limestones and is responsible for the local groundwater recharge of the linear or punctual springs of the area. The main aquifers can be separated or connected with each other depending on the effectiveness of the role that the aquiclude and/or aquitard plays, affected by the low permeability complexes and the fault systems [13]. Based on the tectonic configuration of the area, three hydro-structures have been identified [21] in the Sibillini Mts.…”

“…Isotopic analyses of oxygen of water were performed with a near infrared laser analyzer (L2130i, Picarro, Santa Clara, CA, USA) using the wavelength-scanned cavity ring down spectroscopy technique at the laboratory of INGV of Naples (analytical error δ 18 O ± 0.08‰; data reported vs Vienna Standard Mean Ocean Water, V-SMOW). The determination of the recharge area mean elevation for St1 was obtained by applying the δ 18 O gradient recently published by [13], valid for the entire Sibillini Mt. Massif.…”

“…This study is focused on the effects of the 2016-2017 seismic sequence in the groundwatersurface water interaction of the water basin of the Campiano stream (Umbria Region, Central Italy). In this area, the surface water regime is closely connected with the hydrogeological setting [13][14][15]; the groundwater feeds streams, causing an increase in stream discharge along their course (linear springs) [13]. The socio-economic and environmental context of the area is strongly linked to its relationship with water (hydropower plants, fish farming), making its natural environment a groundwater-dependent ecosystem (GDE) [16].…”

Geochemical Markers as a Tool for the Characterization of a Multi-Layer Urban Aquifer: The Case Study of Como (Northern Italy)

“…Groundwater exploitation for human and industrial use requires the knowledge of the main natural and anthropogenic factors that can affect water quality. Host rock geochemistry and tectonic structural features are natural attributes known to play a major role in groundwater chemical composition and flow path, in addition to the hydrology and geomorphology of the region [4][5][6][7][8]. These attributes, moreover, can greatly affect geochemical background values and can cause high concentrations of potentially toxic elements (PTEs, e.g., As, Ni, Cr, Pb, U, Li), which in turn can negatively affect water quality for human use and consumption [3,[9][10][11].…”

Hydrochemical Characteristics of Groundwater at the Epicenter of the 2021 Biru M6.1 Earthquake in Central Tibet

“…The hydrochemistry of groundwater is generally regulated by precipitation, geological structure, rock type, residence time, and geochemical processes along the groundwater flow paths [1][2][3]. Hydrothermal activities are closely related to deep faults and active faults, and geothermal fluids can rapidly migrate along the fault channels [4,5]. In the processes of earthquake generation and occurrence, changes in the stress conditions of aquifers and mixing of deep and shallow fluids can cause variations in the chemical composition of groundwater in the fault zone and nearby areas [6][7][8][9][10].…”