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Short description:
The Dead Sea transform (DST) is generally attributed to a left lateral shear zone. It connects the spreading centre in the Red Sea with the Taurus collision zone in Turkey over a length of about 1100 km. The tectonic and structural setting of the Dead Sea Transform (DST), specifically within the Dead Sea Basin (DSB, Fig. 1A) and its related basins are topical geoscientific research focuses. Since the late 1970s crustal scale geophysical experiments have been carried out in this region. However, the nature of the crust underlying the eastern and western shoulders of the DSB and the underground of the DST itself is still controversially discussed among researchers. To address one of the central questions of plate tectonics – How do large transform systems work and what are their typical features? – an international geoscientific Dead Sea Integrated Research project (DESIRE) is conducted by colleagues from Germany, Israel, the state of Palestine and Jordan. In order to provide a high resolution aero gravity data base to support 3D numerical modeling and hence a more comprehensive understanding of the nature and segmentation of the DST related basins, an airborne gravity survey as a part of the DESIRE project has been conducted in February to March 2007. The aero gravity survey covers the DST from Elat/Aqaba in the South to the northern rim of the Dead Sea (gray lines in Fig. 1).
3D gravity modelling in the Dear Sea Basin
The new compilation of the DESIRE gravity data with the conventional dataset for the DSB area (Fig. 1) was reinterpreted by (1) using 3D density modelling that incorporated additional information obtained from other geophysical research, (2) allowing for regional and residual trends in the gravity field, and (3) carrying out curvature analysis and Euler deconvolution of the gravity field. These methods enabled us to make detailed resolutions of crustal structures within the DSB. The seismic interpretation, earthquake data analysis, geometric features all combined to assist in the modelling and interpretation of the gravity data, revealing aspects of the crustal structures in the DSB that were useful in providing supplementary constraints for the geological and tectonic synthesis. The thickness of the sedimentary fill overlying the basement in the DSB decreases from 14 kilometres in the vicinity of the Lisan Peninsula to 8 kilometres in the northern and the southern sub-basins. The largest volume of salt rocks is locating beneath the Lisan Peninsula. The others can be seen in the western part of the Dead Sea and in the south-western part of the southern sub-basin (Fig. 3). The shallower micro-earthquake events (depth < 10 km, magnitude < 3.0, red points in Fig. 3), which are registered in the vicinity of the modelled salt rocks, might be associated with the movement of salt rocks in the DSB.
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Figure 1
Flight lines and positions of terrestrial gravity point data are shown here. The colours indicate Free Air anomaly values. The profiles cover gaps in terrestrial gravity data mainly at the eastern side of the Dead Sea Basin (Fig. A). The wide angle and refraction seismic profile of the DESIRE (Mechie et al., 2009) is included. DST: Dead Sea Transform
Figure 2
3D gravity model along a S-N flight line, which has been modified using all available additional information The upper crust in the DSB is composed of sedimentary and salt rocks of Palaeozoic to recent age, overlying a crystalline basement that is reached at a depth of about 14 kilometres in the southern sub-basin and the Lisan Peninsula and about 10 kilometres in the northern sub-basin. The modelled densities were 2,700 kg/m3 for the crystalline basement, 2,620 kg/m3 for the Palaeozoic, 2,470 kg/m3 for the Mesozoic, 2,390 kg/m3 for the Miocene and 2,250 kg/m3 for the recent sediments. The lowest gravity anomaly of approximately -140 x 10-5 m/s2, observed over the Lisan Peninsula, is well explained by the salt rock which has a thickness of about 8 kilometres and a density of 2,080 kg/m3.
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Principal Investigators:
Sungchan Choi, H.-J. Götze, U. Meyer (BGR)
Partners:
Other members of the DESIRE Project.
Funded by:
Deutsche Forschungsgemeinschaft, GO380/24-2,
Projekt DESIRE (DEad Sea Integrated Research Project)
Contacts:
Sungchan Choi: choi[at]geophysik.uni-kiel.de
H.-J. Götze: hajo[at]geophysik.uni-kiel.de
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Figure 3
Spatial distribution of the modelled salt rocks in the DSB compared to the shallower earthquake distribution (red points). The shallower micro-earthquakes registered in the DSB might be associated with the movement of salt rocks in the DSB.
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