Monitoring active fumaroles through time-lapse electrical resistivity tomograms: an application to the Pisciarelli fumarolic field (Campi Flegrei, Italy)

Abstract

Volcanoes are usually monitored through observations of many physical and chemical phenomena. In the most dangerous cases, as the one of the Campi Flegrei caldera (Italy), great amount of data are collected, both in discrete or continuously, and regularly stored. However, how to transform such mass of data in a deeper understanding of the volcano dynamics is still an open question. Dissimilar information are in fact always hard to compare, but just integrating all the available knowledge hazardous events could be prevented in a reliable way. Fluids, as water and gasses mobilized in the subsoil by the heat induced by deep magmatic sources, are widely recognized as the first engine of similar occurrences and the volcanic gas emissions represent, together with the seismic activity, one of the most considered precursors. At the same time, the electrical geophysical methods are the most applied in order to detect and characterize the fluid patterns in the subsoil. So, the integration of geoelectrical and geochemical observations should represent one of the most pursued approach in volcanoes monitoring. On the contrary, standard way to compare such data has been not yet codified. The ERT tomograms capability to individuate that parts of the subsoil where gasses cumulate is well understood in literature. However, we look for indications about its proficiency in associating the electrical resistivity changes relative to these zones, once compared to the geochemical time series, to deep related contributes, distinguishing them from the seasonal ones. The electrical signature of the fluid patterns, reconstructed through a time-lapse ERT approach, could be of relevance to better characterize the volcanic phenomena and their origins. In this paper a first test of ERT and geochemical time series integration was performed to enhance the understanding of the Pisciarelli fumarolic field evolution, now the most active area in the whole Campi Flegrei caldera.