The Dead Sea Rift / Dead Sea Transform acts as a hinge between the
Alpine-Himalayan-Mountain Belt, stretching East-West from the Mediterranean
to Indonesia, and the largest active continental rift system, the
Afro-Arabian Rift System, which runs South-North from East Africa
to the Dead Sea. Except for a mild compressional deformation starting
about 180 Ma ago, the Dead Sea region has remained a stable platform
almost since its formation in the late Proterozoic. This tectonic
stability was only recently (ca. 18 Ma ago) interrupted by the formation
of a transform with a left-lateral motion of about 105 km as of today.
The simplicity of this system, especially in the Arava Valley, the
valley between the Dead Sea and the Red Sea, puts it in strong contrast
to other large transform systems like the North Anatolian Fault System,
which is in the middle of an orogenic belt, and the San Andreas Fault
System, which suffered repeated accretional episodes and the interaction
with a triple junction. The simplicity of the Dead Sea Rift / the
nearly linear Dead Sea Transform provides a natural laboratory to
study and understand transfrom faults, one of the key elements of
plate tectonics together with subduction and rifting. Despite the
central role of this world geological site, up to now no geophysical
profile has crossed the Dead Sea Rift / the Dead Sea Transfrom (DST).
The DEad SEa Rift Transect (DESERT) is a multinational and interdisciplinary
study of the Dead Sea Rift, and the main goal of the DESERT project
is to help address a fundamental question of plate tectonics: How
do shear zones work and what controls them, on different scales?
The project began with field work in February 2000, and first experiments
were completed by the DESERT Team in May 2000. The seismic, seismological,
and magnetotelluric experiments presented here, along with the future
electromagnetic, gravity, magnetic, petrological, geothermal, geodynamic,
and geological studies, will provide the geophysical and geodynamic
frame for further geoscientific research. Within the DESERT project,
scientists from Germany, Israel, Jordan, and the Palestine Territories
joined together for the first time to study the crust and upper mantle,
the main shear zones, and the geodynamics of the DST. Over 30 scientists
of the GFZ, the universities of Potsdam, Kiel, Köln, and Göttingen;
the universities of Tel-Aviv and Jerusalem, the national Ministry
of Infrastructure and the Geophysical Institute of Israel; the Natural
Resources Authority, Jordan; and the An-Najah University in Nablus
and the Palestine Water Authority, Palestine Territories; work together
in this project. The 260 km long transect across the DST traverses
Israel, Jordan, and the Palestine Territories. First results of the
geophysical experiments show - contrary to the expectations - basically
no up-doming of the Moho under the rift, suggesting that the mantle
has played a rather insignificant role in the extension process associated
with the Dead Sea Rift. The role of an 8 km thick structure, imaged
as a band of strong reflectors in the lower crust under the elevated
rift shoulder in Jordan, the dynamics of the rift / transform requires
additional geophysical studies planned for the next year. On the
kilometer scale, a 3-D tomographic image of the fault regions shows
significant changes in seismic P-velocities across the fault, and
the analysis of fault guided waves indicates a low-velocity zone
with a velocity reduction of 15 to 25\% and a thickness of only 10
to 20 meters at the surface location of the Arava Fault. This fault
is also the location where a roughly 1.5 km thick body with very
good conductivity in 2 km depth stops abruptly, possibly indicating
the contact of sediments with saline brines to the west of the fault
with a high velocity body with bad conductivity to the east. urn:nbn:de:kobv:b103-030012