Geochemical patterns of groundwater from the Palomares-Carboneras active fault area aquifers (SE Spain): determination of a network of sensitive sites indicators of seismic events.

The aim of this study is to evaluate the hydrogeochemical parameters of the Palomares-Carboneras active fault zones (SE Spain) aquifers to establish especially sensitive sampling points that could be indicators of seismic activity in the fault zone. We consider these points as a part of a network, for this fault area and others in the South of Spain. With a seasonal and/or continuous sampling, in the future, that may allow us to provide advices of possible seismic events. The eastern part of the Betic Cordillera is a Mediterranean semi-arid zone, with a special sensitivity to climatic fluctuations and human activity. A remarkable scarcity in water resources is evident in this region, making it difficult to find groundwater sampling points. Subsequently, a network has been designed with 33 water sites, selected for availability and proximity to the active fault zones, where the physical-chemical features and isotope contents of the groundwater have been determined. Taking into account the geological complexity, as well as the different hydrogeological paths recognized in the area, three geochemical families of water have been found. (1) Water with high electrical conductivity (up to 14,000 μS/cm), temperatures above 20 °C, and, in some cases, traces of boron. (2) Water with medium electrical conductivity (2,000-3,500 μS/cm), temperatures above 20 °C, and traces of boron. (3) Water with electrical conductivity below 1,000 μS/cm, temperatures below 20 °C, and absence of boron. High temperature waters with presence of boron were selected as indicators of deep water circulation processes that can be connected to the seismic activity of the Palomares-Carboneras active fault zones. According to this study, a selected sensible warning aquifer sites has been established. [ABSTRACT FROM AUTHOR]