Magnetotelluric investigation in the High Agri Valley (southern Apennine, Italy)

M Balasco,A Siniscalchi,T A Stabile,A Giocoli,G Romano,S Piscitelli,S Tripaldi

doi:10.5194/nhess-15-843-2015

Abstract

Abstract. In this paper we present the result of a magnetotelluric (MT) investigation carried out across the High Agri Valley (HAV), southern Italy. Several MT soundings were carried out in order to obtain a ~15 km long 2-D resistivity model with an investigation depth of ~10 km. The main aim was to provide valuable data on the geological and structural setting of the HAV. The MT model was compared with pre-existing geological, geophysical and seismic data. The MT model can be schematized as a superposition of three stack lateral varying layers with different thickness and resistivity values: a surficial low–medium resistivity layer associated with the Quaternary deposits and to the allochthonous units; and a deeper high resistivity layer related to the Apulia Platform, separated by a thin layer connected to the mélange zone and to the Pliocene terrigenous marine deposits. Sharp lateral resistivity variations are interpreted as faults that, on the basis of accurate focal mechanism computations, display normal-faulting kinematics.

Highlights

The High Agri Valley (HAV, Basilicata region, southern Italy) is an intermontane basin of the southern Apennine chain characterized by complex geological setting and by active tectonics, as testified by one of the most destructive earthquakes in this area, the M7.0 1857 Basilicata earthquake (Fig. 1)
In this paper we present the result of a magnetotelluric (MT) investigation carried out across the High Agri Valley (HAV), southern Italy
The MT model can be schematized as a superposition of three stack lateral varying layers with different thickness and resistivity values: a surficial low–medium resistivity layer associated with the Quaternary deposits and to the allochthonous units; and a deeper high resistivity layer related to the Apulia Platform, separated by a thin layer connected to the mélange zone and to the Pliocene terrigenous marine deposits

Summary

Introduction

The High Agri Valley (HAV, Basilicata region, southern Italy) is an intermontane basin of the southern Apennine chain characterized by complex geological setting and by active tectonics, as testified by one of the most destructive earthquakes in this area, the M7.0 1857 Basilicata earthquake (Fig. 1). The first paper shows the regional structural setting as inferred by industry seismic profiles and oil wells; the second one presents the results of a local earthquake tomography related to the 3-D Vp and Vp/Vs distribution of the HAV. The electrical resistivity is correlated with the major geological units and, in particular, is dominated by their porosity and the contained fluids Such MT method peculiarity has been proven in a broad range of applications regarding the studies of the Earth’s interior, playing a crucial role in the characterization of faulted areas both in volcanic (Di Maio et al, 1998; Siniscalchi et al, 2012) and seismic environments (Tank et al, 2005; Bedrosian, 2007; Diaferia et al, 2008; Balasco et al, 2011; Becken and Ritter, 2012; Gabàs et al, 2014). The interpretation of the MT model can resolve some outstanding issues, like the depth of the bedrock below the Quaternary deposits and the deep geometrical characterization of the faults

Geological framework

Magnetotelluric data

Seismicity data

Results and interpretation

Discussion and conclusions