Shallow Structure Of The Araba Fault (Dead Sea Transform) From Seismic Investigations
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  • Radwan J. El-Kelani

The Dead Sea Transform (DST), stretching from the Red Sea to the Tauros-Zagros collision zone, is one of the world's major active continental shear zones, exhibiting a total slip of about 100~km within the last 20~Myr. In the southern part, the Arava fault (AF) is considered to be the main fault strand. Within the DESERT project, the structure of crust and upper mantle in the southern part of the transform was studied by a series of geophysical experiments. Latest seismic investigation was a small-scale high-resolution experiment (receiver distance: 5~m, source distance: 20~m) which provided detailed P wave velocity models (first-break tomography) and reflection images of the shallow subsurface structure ($<1000~m$) along 8 one kilometre long profiles crossing the AF at a 10~km long segment. These images directly complement previous studies at larger scale and the analysis of explosion generated guided waves in the same area. We observe a strong cross-fault velocity contrast at depths greater than 1~km, with higher velocities east and lower velocities west of the fault (which we relate to the sedimentary basin fill). In the uppermost layers ($<100~m$) the velocity images appear in part patchy, on some profiles the AF seems to distinguish domaines with different velocities. Even in the high-resolution tomographic pictures we see no indication for a fault-zone related low-velocity zone, but guided waves suggest that at some segments the fault shows a very narrow subvertical low-velocity layer ($<20~m$ wide). Our results suggest that the uppermost part of the AF is characterized by a very narrow damage zone. This can be explained by the fact that the total slip within the DST system is/was distributed in space and time over several fault strands, resulting in a reduced slip on the currently active strand of the AF. Furthermore, the shallow velocity structure probably reflects the interaction of movement along the fault and the deposition of sediments. 

Eos Trans. AGU, 83(47), Fall Meet. Suppl
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