Shallow to intermediate resistivity features of the Colfiorito Fault System inferred by DC and MT survey

I. Diaferia, M. Loddo, D. Schiavone, A. Siniscalchi

Abstract


Over the last decade electromagnetic (EM) measurements have provided new constraints on the upper-crustal
structure of the major fault zones in the world, both when they act as conduit and as a barrier, due to strong sensitivity
of resistivity to fluids circulation and mineralization. On the track of a high impact magnetotelluric (MT)
study performed across the San Andreas Fault, high resolution EM data were collected in the Colfiorito epicentral
area along profiles crossing some main fault lineaments. Being the study focussed both on shallow that on intermediate
resistivity distribution in the brittle upper-crust, a MT profile was integrated by several electrical resistivity
tomographies (ERT). The latter were successful in locating faults even where the structures are buried by a wide
covering of Quaternary deposits and in the recognition of different electrical signatures of the faults. MT resistivity
model crossing Mt. Prefoglio normal fault clearly imaged the typical thrust structures of the area and a high
conductive zone spatially related to the fault. Seismicity seems to be located outside such conductive area, whose
behaviour suggests a fluidised and altered zone incapable of supporting significant stress internally.

Keywords


Colfiorito fault system;magnetotellurics;geoelectrics;fluids

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References


DOI: https://doi.org/10.4401/ag-3031
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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X