Towards the Understanding of Hydrogeochemical Seismic Responses in Karst Aquifers: A Retrospective Meta-Analysis Focused on the Apennines (Italy)

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.

Integration of photogrammetry from unmanned aerial vehicles, field measurements and discrete fracture network modeling to understand groundwater flow in remote settings: test and comparison with geochemical markers in an Alpine catchment

“…7c), Mg does not correlate with Ca and other trace elements; instead it shows a correlation with EC and carbonates, because this element shows a general high concentration in all the water samples. This case study confirms the potential of PCA for geochemical analysis of water samples (Binda et al 2020b;Gambillara et al 2013;Giussani et al 2016;Rosen et al 2018).…”

Hydrogeochemistry of Hot Springs and the 2018 Mojiang M 5.9 Earthquake-Related Chemical Changes in the Simao Basin, China

“…Moreover, the water chemistry of No.7 and No.13 sites also recovered. Although the vigorous water-interaction model is used to explain the changes in the chemical components (i.e., major and trace elements) following an earthquake, the model fails to explain the variables that indicate water mixing or interactions with deep fluids (e.g., water isotopes, dissolved gases and reservoir temperature; Binda et al, 2020).…”

“…Seismic waves may enhance the permeability of the affected aquifers through increasing fracture porosity, changing pore pressure, and fracturing aquitards. These seismic effects could result in the mixing of fluids from different aquifers or the upwelling of deep fluids (Binda et al, 2020). Before the occurrence of the Mojiang earthquake (from April to July 2018), the compressive activity was significantly greater around the Jingdong-Simao region (Yang et al, 2019).…”

Characteristics and Sources of Selected Halocarbon and Hydrocarbon Volatile Organic Compounds in Surface Water of the Han River Basin

“…PCA is a common multivariate statistical approach used to determine the relationships among several interrelated variables, wherein the variables with comparable properties are grouped into a same principal component (PC) [12,46,47]. Therefore, PCA is a useful method for the interpretation of chemical trends in water bodies and groundwater [48,49]. Four VOCs having a detection frequency of 10% or more (chloroform, PCE, TCE, and xylenes) were selected as the variables.…”