The crustal structure of the Dead Sea Transform

Abstract

S U M M A R YTo address one of the central questions of plate tectonics-How do large transform systems work and what are their typical features?-seismic investigations across the Dead Sea Transform (DST), the boundary between the African and Arabian plates in the Middle East, were conducted for the first time. A major component of these investigations was a combined reflection/refraction survey across the territories of Palestine, Israel and Jordan. The main results of this study are: (1) The seismic basement is offset by 3-5 km under the DST, (2) The DST cuts through the entire crust, broadening in the lower crust, (3) Strong lower crustal reflectors are imaged only on one side of the DST, (4) The seismic velocity sections show a steady increase in the depth of the crust-mantle transition (Moho) from ∼26 km at the Mediterranean to ∼39 km under the Jordan highlands, with only a small but visible, asymmetric topography of the Moho under the DST. These observations can be linked to the left-lateral movement of 105 km of the two plates in the last 17 Myr, accompanied by strong deformation within a narrow zone cutting through the entire crust. Comparing the DST and the San Andreas Fault (SAF) system, a strong asymmetry in subhorizontal lower crustal reflectors and a deep reaching deformation zone both occur around the DST and the SAF. The fact that such lower crustal reflectors and deep deformation zones are observed in such different transform systems suggests that these structures are possibly fundamental features of large transform plate boundaries.

The Levantine Basin—crustal structure and origin

“…An abrupt transition is not observed on either line, but the rise of the Moho from 26 to 22 km on line P2 and from 27 km (Weber et al, 2004) near Gaza to 22 km on line P1 could mark a zone with a gradual transition from continental to oceanic crust. Such a transition zone has been observed elsewhere, e.g., at the Hatton margin offshore Ireland (Vogt et al, 1998), at the Flemish Cap off New Foundland (Funck et al, 2004) and in Nova Scotia (Funck et al, 2004).…”

“…A compilation of the results of the DESERT2000-project (Weber et al, 2004), profile III of the study of BenAvraham et al (2002) and our line P1 (Fig. 16), which are almost in line (Fig.…”

“…On all these lines, accompanying gravity and magnetic models were compiled, which based on the refraction seismic models and showed matching results. Deep seismic experiments analysing the crust under Israel, Negev and Jordan have been carried out by Ginzburg et al (1979Ginzburg et al ( , 1994, El-Isa et al (1987) and, recently, in the frame of the DESERT2000 project (Weber et al, 2004) (Fig. 1) and show a crustal thickness under Judea of less than 30km, thinning to the north to slightly over 20km under Galilee-Lebanon and thickening to the south and east to up to 40km beneath Negev and Jordan.…”

“…1). Further deep seismic studies have been carried out onshore by Ginzburg et al (1979Ginzburg et al ( , 1994, El-Isa et al (1987) and, recently, the DESERT2000 project (Weber et al, 2004), providing information on the crustal structure under Israel, Jordan and the Sinai Peninsula.…”

Dead Sea Basin Imaged by Ambient Seismic Noise Tomography

“…Following the success of the international multi-disciplinary geoscientific project DESERT (Weber et al, 2004; stations employed short period sensors (1 Hz Mark L4 seismometers), though some broad band (Guralp 40-T, 3-T and Streckeisen STS2) seismometers were also used. Data were continuously recorded in the field at 100 Hz and 200 Hz for the broad band and short period stations, respectively.…”