DOI: 10.2312/GFZ.b103-09084 Publisher: GFZ German Research Centre for Geosciences, Potsdam, Germany
Since the advent of plate-tectonics the Dead Sea Transform (DST) has been considered a prime site to examine geodynamic processes. It has accommodated a total of 105 km of left-lateral transform motion between the African and Arabian plates since early Miocene (~20 My). Large historical earthquakes on the DST with magnitudes up to 7 and the 1995 Nueiba M7.2 event, as well as ongoing micro-seismic activity show that the DST is a seismically active plate boundary. The DST therefore poses a considerable seismic hazard to Palestine, Israel, and Jordan. The DST segment between the Dead Sea and the Red Sea, called Arava/Araba Fault (AF), is studied in DESERT in detail, using a multi-disciplinary and multi-scale approach from the micrometer to the plate-tectonic scale. This volume contains the results of the DESERT project running from 2000 to 2006. It opens with a review paper followed by 33 special papers. Available at http://dx.doi.org/10.2312/GFZ.b103-09084 (open access).
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[Show abstract][Hide abstract]ABSTRACT: The Dead Sea Rift Transect (DESERT 2000) is a multinational and interdisciplinary study of the Dead Sea Rift. The project began field work in February 2000 and the first experiments were successfully completed in May. The seismic, seismological, and magnetotelluric experiments presented here, along with the future electromagnetic, gravity, magnetic, geodynamic, and geological studies, will provide the basic geophysical frame for further geoscientific research. DESERT 2000 should also help to address a fundamental question of plate tectonics: How do shear zones work and what controls them?
Full-text · Article · Dec 2000 · Eos Transactions American Geophysical Union
[Show abstract][Hide abstract]ABSTRACT: The Dead Sea Transform (DST) is a major plate boundary separating the African and Arabian plates. It extends over 1000 km from the Red Sea rift in the south to the Taurus collision zone in the north. Present-day left-lateral motion is 4±2 mm/year which is consistent with the kinematics of the Arabian plate assuming a rotation rate of about 0.4°/Ma around a pole at 31.1°N and 26.7°E relative to Africa. The DST became active about 18-21 Ma ago and since then, it has accommodated about 100 km of left-lateral slip. In the area between the Dead Sea and Red Sea the DST is marked by the Arava fault which may have the potential to produce Mw ~ 7 earthquakes along some of its segments about every 200 years. The aim of the interdisciplinary and multi-scale Dead Sea Rift Transect (DESERT) project is to shed light on the question of how large shear zones work. DESERT consists of several geophysical sub-projects that are carried out by partners in Germany, Israel, Jordan and Palestine. Principal investigators are Michael Weber in Germany, Zvi Ben-Avraham in Israel, Khalil Abu-Ayyash in Jordan, and Radwan El-Kelani in the Palestine Territories. One of the sub-projects was a large-scale passive seismic experiment which was conducted in Israel, Jordan, and the territory of the Palestinian Authority. Aims of the project are (a) study of crust and mantle structure with the receiver function (RF) method, (b) travel-time tomography, (c) to investigate azimuthal anisotropy in crust and upper mantle from shear wave splitting, and (d) the study of local seismicity. In this note, we give a brief overview on the field experiment and the data archiving procedure.
[Show abstract][Hide abstract]ABSTRACT: Lithospheric-scale transform faults play an important role in the dynamics of global plate motion. Near-surface deformation fields for such faults are relatively well documented by satellite geodesy, strain measurements and earthquake source studies, and deeper crustal structure has been imaged by seismic profiling. Relatively little is known, however, about deformation taking place in the subcrustal lithosphere--that is, the width and depth of the region associated with the deformation, the transition between deformed and undeformed lithosphere and the interaction between lithospheric and asthenospheric mantle flow at the plate boundary. Here we present evidence for a narrow, approximately 20-km-wide, subcrustal anisotropic zone of fault-parallel mineral alignment beneath the Dead Sea transform, obtained from an inversion of shear-wave splitting observations along a dense receiver profile. The geometry of this zone and the contrast between distinct anisotropic domains suggest subhorizontal mantle flow
[Show abstract][Hide abstract]ABSTRACT: High-resolution seismic tomography and magneto-telluric (MT) soundings of the shallow crust show strong changes in material properties across the Dead Sea Transform Fault (DST) in the Arava valley in Jordan. 2D inversion results of the MT data indicate that the DST is associated with a strong lateral conductivity contrast of a highly conductive layer at a depth of approximately 1.5 km cut-off at a position coinciding with the surface trace of the DST. At the same location, we observe a sharp increase of P wave velocities from <4 km/s west of the fault to >5 km/s to the east. The high velocities in the east probably reflect Precambrian rocks while the high electrical conductivity west of the DST is attributed to saline fluids within the sedimentary filling. In this sense, the DST appears to act as an impermeable barrier between two different rock formations. Such a localized fluid barrier is consistent with models of fault zone evolution but has so far not been imaged by geophysical methods. The situati
Full-text · Article · Jul 2003 · Geophysical Research Letters
[Show abstract][Hide abstract]ABSTRACT: On several recordings of linear seismometer arrays crossing the Arava Fault (AF) in the Middle East, we see prominent wave trains emerging from in-fault explosions which we interpret as waves being guided by a fault zone related low-velocity layer. The AF is located in the Arava Valley and is considered the principal active fault of the mainly N-S striking Dead Sea Transform System in this section. Observations of these wave trains are confined to certain segments of the receiver lines and occur only for particular shot locations. They exhibit large amplitudes and are almost monochromatic. We model them by a two-dimensional (2-D) analytical solution for the scalar wave field in models with a vertical waveguide embedded in two quarter spaces. A hybrid search scheme combining genetic algorithm and a local random search is employed to explore the multimodal parameter space. Resolution is investigated by synthetic tests. The observations are adequately fit by models with a narrow, only 3-12 m wide waveguide with S wave velocity reduced by 10-60% of the surrounding rock. We relate this vertical low-velocity layer with the damage zone of the AF since the location of receivers observing and of shots generating the guided waves, respectively, match with the surface trace of the fault. The thickness of the damage zone of the AF, at least at shallow depths, seems to be much smaller than in other major fault zones. This could be due to less total slip on this fault.
Full-text · Article · Jul 2003 · Journal of Geophysical Research Atmospheres
[Show abstract][Hide abstract]ABSTRACT: To 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.
Full-text · Article · Mar 2004 · Geophysical Journal International
[Show abstract][Hide abstract]ABSTRACT: Seismic waveforms recorded at high-density receiver arrays facilitate the application of new inversion techniques, which take advantage of the coherent nature of the observations. We use measurements of shear wave splitting parameters from observed SKS waveforms along a dense receiver profile and compare them with splitting parameters obtained from numerical waveform modeling through anisotropic Earth models. We use two different iterative approaches for the inversion of the observed splitting parameters (1) a local optimization technique (the downhill simplex method) and (2) a global genetic algorithm search. In our forward modeling, we calculate SKS waveforms by a finite difference (FD) method solving the anisotropic wave equation, instead of deriving individual anisotropic models for each station and combining them into one model. By the comparison of FD modeling and observations we avoid a direct interpretation of the splitting parameters in terms of medium properties. We apply these techniques to
No preview · Article · Mar 2005 · Journal of Geophysical Research Atmospheres