An-Najah Staff

How do shear zones work and what controls them ? To be able to address this central question of plate tectonics, the DEad SEa Rift Transect (DESERT) group performed an interdisciplinary and multi-scale study of the Dead Sea Rift. DESERT consists of several coincident seismic, magnetotelluric and seismological sub-projects performed by partners from Germany, Israel, Jordan and Palestine. The Dead Sea Rift / Dead Sea Transform acts as the hinge between the Alpine-Himalayan mountain belt and the Afro-Arabian rift system and has a left-lateral motion of about 105 km as of today. The nearly linear structure of this world geological site provides a natural laboratory to study large active faults. The key to understanding the geodynamics and plate tectonics in this region, is a detailed knowledge of the crustal and upper mantle structure on scales from plate tectonics to meters. This presentation will give an overview of the results of the seismic/seismological and magnetotelluric sub-projects of DESERT: (a) Wide-angle reflection/refraction; (b) Near-vertical reflection; (c) Controlled source array; (d) Passive seismological array; (e) Magnetotelluric pilot-study. One result on the plate tectonic scale is that the Moho depth gradually increases from 28 to 38 km along the profile, but that no Moho updoming is observed under the "rift". Therefore it seems that the mantle only played a minor role in the extension process associated with the rift. On the meter scale it was possible to excite fault guided waves which indicate that the low-velocity zone associated with the fault zone shows a velocity reduction of 10 to 25 \%, but only a width of 10 to 20 meters.