Abstract
With controlled seismic sources and specifically designed receiver
arrays, we image a subvertical boundary between two lithological
blocks at the Arava Fault (AF) in the Middle East. The AF is the
main strike-slip fault of the Dead Sea Transform (DST) in the segment
between the Dead Sea and the Red Sea. Our imaging (migration) method
is based on array beamforming and coherence analysis of P to P scattered
seismic phases. We use a 1-D background velocity model and the direct
P arrival as a reference phase. Careful resolution testing is necessary,
because the target volume is irregularly sampled by rays. A spread
function describing energy dispersion at localized point scatterers
and synthetic calculations for large planar structures provides estimates
of the resolution of the images. We resolve a 7 km long steeply dipping
reflector offset roughly 1 km from the surface trace of the AF. The
reflector can be imaged from about 1 km down to 4 km depth. Previous
and ongoing studies in this region have shown a strong contrast across
the fault: low seismic velocities and electrical resistivities to
the west and high velocities and resistivities to the east of it.
We therefore suggest that the imaged reflector marks the contrast
between young sedimentary fill in the west and Precambrian rocks
in the east. If correct, the boundary between the two blocks is offset
about 1 km east of the current surface trace of the AF.
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