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Title: A magnetotelluric survey in Methana Peninsula (Greece)
Author: Volti, Theodora
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1996
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As a first deep geophysical survey, thirteen magnetotelluric (MT) and magnetovariation (MV) soundings in the period range of 0.0085 - 6000 s have been carried out in the Methana Peninsula and Trizina area (Greece) which form a part of the active Hellenic Volcanic Arc (HVA). The intensity of artificial disturbances in Methana prevented the acquisition of good quality data, and led to the exclusion of data in the 10-100 s range from further interpretation. The measured data are first processed using robust methods, then decomposed using the methods of Groom and Bailey and of Bahr. Thin sheet modelling follows with the aim of detecting effects due to the surrounding seas. All the data show anisotropy and were found to be distorted by galvanic distortion, facts which become more apparent at periods below 1 s. At the same period, effects from the sea also become important. The above problems indicated: (i) the insufficiency of 1-D modelling (ii) that the data are at least 2-D and (iii) that a careful consideration of all the above effects must be given in order to provide a meaningful electrical model. The analysis of distortion effects and the measured induction arrows enable the determination of a regional azimuth to which subsequently the data are rotated. Seven sites are used, and a 2-D model is proposed. The model indicates a zone of high conductivity (7-32 ohm m) beneath the centre of the peninsula at a depth of 1-5 km, which is interpreted as being connected with the volcanic history of Methana, as a remaining and cooling part of former magmatic activity. Although with the long period MT data it was not possible to locate a deep magma source connected with the indicated anomaly, induction arrows at T > 2400 s taken from the regional area point towards the South and South West, perpendicular to the strike of the well known deep structure of the Hellenic Volcanic Arc. Further attempts to integrate the results from Methana with other areas along the HVA lead to correlation of the regional azimuths with horizontal stress directions in the South Aegean sea.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available