MAGNETOTELLURIC SOUNDING AT THE PETROPAVLOVSK GEODYNAMIC TEST SITE, KAMCHATKA

Abstract

Some 1000 MT soundings at the Petropavlovsk Geodynamic Test Site were analyzed. The curves were classified by directions along and across the major structural zones. The longitudinal and transverse MT curves were found to have been affected by local galvanic effects. These effects were suppressed by statistical averaging. A qualitative interpretation of the resulting average curves which were largely free from local galvanic effects allowed a division of the site area into zones having different electrical conductivities at depth: a western zone having a well-pronounced crustal layer of high conductivity and an eastern one, close to the Benioff zone, where this layer was not identified. Active volcanoes are confined to a boundary between these two zones. Further quantitative interpretation of MT curves can only be done using 3-D numerical and physical modeling.