Earthquake-Induced Spring Discharge Modifications: The Pescara di Arquata Spring Reaction to the August–October 2016 Central Italy Earthquakes

Daniela Valigi,Giulio Beddini,Carlo Cardellini,Lucia Mastrorillo,Costanza Cambi,Roberto Checcucci,Davide Fronzi,Alberto Tazioli,Francesco Mirabella

doi:10.3390/w12030767

Abstract

Co-seismic changes in groundwater regime are often observed after moderate to strong earthquakes. The 24 August 2016 Mw 6.0 extensional Amatrice earthquake, which was the first event of a long-lasting seismic sequence, including the 30 October 2016 Mw 6.5 Norcia event, triggered a significant discharge alteration to the Pescara di Arquata spring, located in the Umbria-Marche Apennines (Northern Apennines, Central Italy) and exploited for drinking purposes. During the first five months after the first mainshock, an extra flow of about 30% was recorded, while both water chemistry and temperature did not show significant changes. Thereafter, the spring discharge decreased significantly, and at the end of 2019 it was still lower than normal. The Standardized Precipitation Index (SPI) indicates that these low mean monthly discharge values are not related to particularly dry conditions. The increase in post-seismic depletion coefficients indicates that the aquifer empties faster than it did during the inter-seismic period. The observed transient increase and subsequent decrease of discharge are consistent with a transient, earthquake-related increase in hydraulic conductivity.

Highlights

Earthquakes are historically known to cause hydrogeological modifications, including changes in chemical composition [1,2], streamflow [3,4,5,6,7,8,9], and spring characteristics [10,11]
Physical parameters and chemical concentrations of major elements of the Pescara di Arquata spring water collected from 30 August 2016 are reported in Table 3, together with bibliographic data ara ara ara na 7.6 na
1.53 referred to the7.8 to 2009 [40,50] and with data of other springs located on the eastern ara 30 August

Summary

Introduction

Earthquakes are historically known to cause hydrogeological modifications, including changes in chemical composition [1,2], streamflow [3,4,5,6,7,8,9], and spring characteristics [10,11]. Long-lasting spring and stream excess flows are known to accompany major normal faults and strike-slip faults earthquakes [9,10,11], discharge increases have been detected for thrust faults induced earthquakes (see, for example [5,12]). According to Sibson [13], for normal faults, fluid movement is favored along the fault strike (along the σ2) during the inter-seismic period when the fault surface mainly behaves as a barrier. Esposito et al [19] described, among others, the consequences of the 1980 Irpinia earthquake, which caused hydrogeological effects as far as 200 km; in particular, a significant increase of the Caposele spring flow was observed, which returned to normal conditions after about one year

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Conclusion