A magnetotelluric survey southwards from the Bodmin granite

This report describes a reconnaissance MagnetoTelluric (MT) survey carried out in early 1993 as part of the TMOS mapping programme of the Plymouth sheet in SW England. An 8 site survey, along a N-S profile extending from near the coast onto the Bodmin granite was conducted during an 8 day field programme. The purpose of the survey was to investigate the relevance of the MT method to mapping the configuration of the geological units at depth. The MT method provides geological information by modelling the subsurface resistivity distribution, usually along a profile. In order to provide valid structural assessments the data modelling must take into account the observed data characteristics. The present initial report provides information on the survey, the measurements undertaken and the data obtained. The subsurface structure across the profile is assessed using geoelectric strike directions, one-dimensional (l-D) inversion and two-dimensional (2-D) inversion.