Groundwater circulation and earthquake-related changes in hydrogeological karst environments: a case study of the Sibill
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Groundwater circulation and earthquake-related changes in hydrogeological karst environments: a case study of the Sibillini Mountains (central Italy) involving artificial tracers T. Nanni 1 & P. M. Vivalda 1 & S. Palpacelli 2 & M. Marcellini 1 & A. Tazioli 1 Received: 27 September 2019 / Accepted: 26 June 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Using artificial tracer tests, this study confirms the presence of a single basal aquifer feeding the springs in the wide and complex hydrogeological boundary of the Sibillini Mountains of central Italy. The tracer was introduced into the sinkhole of the Castelluccio di Norcia plain. The tracer test results, observed at the studied springs, highlight the changes induced by the 2016/2017 earthquake in the water circulation of the aquifer system. In particular, the seismic events increased the hydraulic conductivity of the basal aquifer, with a consequent increase in the springs’ flow rates at the western hydrogeological boundary and a decrease in the flow rates at the eastern Adriatic hydrogeological boundary. This phenomenon is in accordance with the hydro-structural framework of the area. The study also investigated the relation between groundwater circulation and tracer behaviour in the springs during the pre- and post-earthquake periods. The tracer test results led to the formulation of hypotheses about water circulation of the area. The trend of the tracer breakthrough curves demonstrates that the upper portion of the basal aquifer is characterised by fast water circulation similar to that in the epiphreatic area of karst aquifers, while a slow circulation due to fissures with interconnected drains occurs in the deepest portion of the aquifers. The obtained results highlight how tectonics and karst can affect the hydrogeological setting of the Apennine carbonate chain; in particular, the seismicity of central Italy may alter groundwater circulation for a long period of time when great magnitude earthquakes occur. Keywords Carbonate rocks . Earthquake . Fractured rocks . Tracer tests . Italy
Introduction and purpose of the work This study examines the characteristics of groundwater flow paths in the very large hydrogeological complex of the Sibillini Mountains (extended over approximately 60 km2), located in the southern area of the Umbria-Marche Apennines in Italy (Fig. 1), which is characterised by a complicated morphological and structural setting (Giovagnotti 1975; Coltorti and Farabollini 1995; Pierantoni et al. 2013; Aringoli et al. 2014), a vast areal extension and a complex
* A. Tazioli [email protected] 1
Università Politecnica delle Marche, department SIMAU, via Brecce Bianche 12, 60131 Ancona, Italy
2
Treia, Italy
hydro-stratigraphy with several separate aquifers (Boni et al. 1986; Boni 2010). The aquifers feed springs with flow rates higher than 0.6 m3/s and linear springs with flow rates that reach a total of approximately 5.0 m3/s. These aquifers are of great importance as drinking water supply for a
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