Geophysical images of the Dead Sea Transform in Jordan reveal an impermeable barrier for fluid flow

Abstract

High- resolutionseismictomography and magnetotelluric (MT) soundings of the shallow crust show strong changes in material properties across the Dead Sea Transform Fault (DST) in the Arava valley in Jordan. 2D inversion results of the MT data indicate that the DST is associated with a strong lateral conductivity contrast of a highly conductive layer at a depth of approximately 1.5 km cut-off at a position coinciding with the surface trace of the DST. At the same location, we observe a sharp increase of P wave velocities from <4 km/s west of the fault to >5 km/s to the east. The high velocities in the east probably reflect Precambrian rocks while the high electrical conductivity west of the DST is attributed to saline fluids within the sedimentary filling. In this sense, the DST appears to act as an impermeable barrier between two different rock formations. Such a localized fluid barrier is consistent with models of fault zone evolution but has so far not been imaged by geophysical methods. The situation at the DST is remarkably different from active segments of the San Andreas Fault which typically show a conductive fault core acting as a fluid conduit.