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Articles & Research
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Data Resources Category
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Data Resources Category |
Scientific Paper |
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Research
Title |
Crustal shear velocity structure across the Dead Sea Transform from two-dimensional modelling of DESERT project explosion seismic data |
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Published by
(sources) |
Geophysical Journal International, 160, 3, 910-924 |
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Carried out by
(authors) |
Ayman Mohsen |
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Issue Year |
2005 |
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Abstract |
An analysis of the shear (S) waves recorded
during the wide-angle reflection/refraction (WRR) experiment as part of the
DESERT project crossing the Dead Sea Transform (DST) reveals average crustal
S-wave velocities of 3.3-3.5 km s-1 beneath the WRR profile. Together with
average crustal P-wave velocities of 5.8-6.1 km s-1 from an already published
study this provides average crustal Poisson's ratios of 0.26-0.27 (Vp/Vs=
1.76-1.78) below the profile. The top two layers consisting predominantly of
sedimentary rocks have S-wave velocities of 1.8-2.7 km s-1 and Poisson's ratios
of 0.25-0.31 (Vp/Vs= 1.73-1.91). Beneath these two layers the seismic basement
has average S-wave velocities of around 3.6 km s-1 east of the DST and about
3.7 km s-1 west of the DST and Poisson's ratios of 0.24-0.25 (Vp/Vs=
1.71-1.73). The lower crust has an average S-wave velocity of about 3.75 km s-1
and an average Poisson's ratio of around 0.27 (Vp/Vs= 1.78). No Sn phase
refracted through the uppermost mantle was observed. The results provide for
the first time information from controlled source data on the crustal S-wave
velocity structure for the region west of the DST in Israel and Palestine and
agree with earlier results for the region east of the DST in the Jordanian
highlands. A shear wave splitting study using SKS waves has found evidence for
crustal anisotropy beneath the WRR profile while a receiver function study has
found evidence for a lower crustal, high S-wave velocity layer east of the DST
below the profile. Although no evidence was found in the S-wave data for either
feature, the S-wave data are not incompatible with crustal anisotropy being
present as the WRR profile only lies 30� off the proposed symmetry axis of
the anisotropy where the difference in the two S-wave velocities is still very
small. In the case of the lower crustal, high S-wave velocity layer, if the
velocity change at the top of this layer comprises a small first-order
discontinuity underlain by a 2 km thick transition zone, instead of just a
large first-order discontinuity, then both the receiver function data and the
WRR data presented here can be satisfied. Finally, the S-wave velocities and
Poisson's ratios which have been derived in this study are typical of
continental crust and do not require extensional processes to explain them.
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