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Articles & Research
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Data Resources Category
Data Resources Category |
Scientific Paper |
Research
Title |
Anatomy of the Dead Sea transform from lithospheric to microscopic scale |
Published by
(sources) |
Reviews of Geophysics, 47, RG2002 |
Carried out by
(authors) |
Ayman Mohsen |
Issue Year |
2009 |
Abstract |
Fault zones are the locations where motion of tectonic
plates, often associated with earthquakes, is accommodated. Despite a rapid
increase in the understanding of faults in the last decades, our knowledge of
their geometry, petrophysical properties, and controlling processes remains
incomplete. The central questions addressed here in our study of the Dead Sea
Transform (DST) in the Middle East are as follows: (1) What are the structure
and kinematics of a large fault zone? (2) What controls its structure and
kinematics? (3) How does the DST compare to other plate boundary fault zones?
The DST has accommodated a total of 105 km of left‐lateral
transform motion between the African and Arabian plates since early Miocene (∼20 Ma). The
DST segment between the Dead Sea and the Red Sea, called the Arava/Araba Fault
(AF), is studied here using a multidisciplinary and multiscale approach from
the μm to the plate tectonic scale. We observe that under the DST a narrow,
subvertical zone cuts through crust and lithosphere. First, from west to east
the crustal thickness increases smoothly from 26 to 39 km, and a subhorizontal
lower crustal reflector is detected east of the AF. Second, several faults
exist in the upper crust in a 40 km wide zone centered on the AF, but none have
kilometer‐size zones of decreased seismic velocities or zones of
high electrical conductivities in the upper crust expected for large damage
zones. Third, the AF is the main branch of the DST system, even though it has
accommodated only a part (up to 60 km) of the overall 105 km of sinistral plate
motion. Fourth, the AF acts as a barrier to fluids to a depth of 4 km, and the
lithology changes abruptly across it. Fifth, in the top few hundred meters of
the AF a locally transpressional regime is observed in a 100–300 m wide zone of
deformed and displaced material, bordered by subparallel faults forming a
positive flower structure. Other segments of the AF have a transtensional
character with small pull‐aparts along them. The damage
zones of the individual faults are only 5–20 m wide at this depth range. Sixth,
two areas on the AF show mesoscale to microscale faulting and veining in
limestone sequences with faulting depths between 2 and 5 km. Seventh, fluids in
the AF are carried downward into the fault zone. Only a minor fraction of
fluids is derived from ascending hydrothermal fluids. However, we found that on
the kilometer scale the AF does not act as an important fluid conduit. Most of
these findings are corroborated using thermomechanical modeling where shear
deformation in the upper crust is localized in one or two major faults; at
larger depth, shear deformation occurs in a 20–40 km wide zone with a
mechanically weak decoupling zone extending subvertically through the entire
lithosphere.
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