Abstract
Earthquakes are known to affect groundwater properties, yet the mechanisms causing chemical and physical aquifer changes are still unclear. The Apennines mountain belt in Italy presents a rich literature of case studies documenting hydrogeochemical response to seismicity, due to the high frequency of seismic events and the presence of different regional aquifers in the area. In this study, we synthesize published data from the last 30 years in the Apennine region in order to shed light on the main mechanisms causing earthquake induced water changes. The results suggest the geologic and hydrologic setting specific to a given spring play an important role in spring response, as well as the timing of the observed response. In contrast to setting, the main focal mechanisms of earthquake and the distance between epicenter and the analyzed springs seems to present a minor role in defining the response. The analysis of different response variables, moreover, indicates that an important driver of change is the degassing of CO2, especially in thermal springs, whereas a rapid increase in solute concentration due to permeability enhancement is observable in different cold and shallow springs. These findings also leave open the debate regarding whether earthquake precursors can be recognized beyond site-specific responses. Such responses can be understood more comprehensively through the establishment of a regional long-term monitoring system and continuous harmonization of data and sampling strategies, achievable in the Apennine region through the set-up of a monitoring network.
Highlights
Major earthquakes (Mw 6.0 and above) are catastrophic events that can dramatically impact human beings, human infrastructure, and the environment [1]
Adriatic foredeep domains characterized by a compressional tectonic regime; (4) thrust belt units accreted during the Alpine orogenesis in the Alps and in Corsica; (5) areas affected by extensional accreted during theareas
The major changes observed during the 2012 Emilia earthquake are similar to the responses of the seismic sequences in the central Apennines: anomalous increase of dissolved gases especially in deep wells [65], presumably derived from deep-seated fluid interaction, and a slight increase in major ions observed in shallower karst aquifers [99]
Summary
Major earthquakes (Mw 6.0 and above) are catastrophic events that can dramatically impact human beings, human infrastructure, and the environment [1]. The first published observations of coseismic chemical responses were conducted in the late 1960s [16], followed by case studies of hydrochemical anomalies reported worldwide during events in 1990s and 2000s [17,18,19,20,21]. It seems that in recent years, knowledge about earthquake effects on water resources has advanced as more precise and inexpensive monitoring systems have become available. We present a meta-analysis of data from Apennines case studies covering 5 seismic sequences during last 40 years to provide an enhanced understanding of the various phenomena causing hydrogeochemical responses to medium and large earthquakes, including the relationship to hydrogeologic and tectonic setting
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