@article{StankiewiczWeberMohsenetal.2012, author = {Stankiewicz, Jacek and Weber, Michael H. and Mohsen, Ayman and Hofstetter, Rami}, title = {Dead Sea Basin imaged by ambient seismic noise tomography}, series = {Pure and applied geophysics}, volume = {169}, journal = {Pure and applied geophysics}, number = {4}, publisher = {Springer}, address = {Basel}, issn = {0033-4553}, doi = {10.1007/s00024-011-0350-y}, pages = {615 -- 623}, year = {2012}, abstract = {In the framework of the Dead Sea Integrated Research project (DESIRE), 59 seismological stations were deployed in the region of the Dead Sea Basin. Twenty of these stations recorded data of sufficiently high quality between May and September 2007 to be used for ambient seismic noise analysis. Empirical Green's functions are extracted from cross-correlations of long term recordings. These functions are dominated by Rayleigh waves, whose group velocities can be measured in the frequency range from 0.1 to 0.5 Hz. Analysis of positive and negative correlation lags of the Green's functions makes it possible to identify the direction of the source of the incoming energy. Signals with frequencies higher than 0.2 Hz originate from the Mediterranean Sea, while low frequencies arrive from the direction of the Red Sea. Travel times of the extracted Rayleigh waves were measured between station pairs for different frequencies, and tomographically inverted to provide independent velocity models. Four such 2D models were computed for a set of frequencies, all corresponding to different sampling depths, and thus together giving an indication of the velocity variations in 3D extending to a depth of 10 km. The results show low velocities in the Dead Sea Basin, consistent with previous studies suggesting up to 8 km of recent sedimentary infill in the Basin. The complex structure of the western margin of the Basin is also observed, with sedimentary infill present to depths not exceeding 5 km west of the southern part of the Dead Sea. The high velocities associated with the Lisan salt diapir are also observed down to a depth of similar to 5 km. The reliability of the results is confirmed by checkerboard recovery tests.}, language = {en} } @article{StankiewiczMunozRitteretal.2011, author = {Stankiewicz, Jacek and Munoz, G. and Ritter, Oliver and Bedrosian, Paul A. and Ryberg, Trond and Weckmann, Ute and Weber, Michael H.}, title = {Shallow lithological structure across the Dead Sea Transform derived from geophysical experiments}, series = {Geochemistry, geophysics, geosystems}, volume = {12}, journal = {Geochemistry, geophysics, geosystems}, number = {3-4}, publisher = {American Geophysical Union}, address = {Washington}, issn = {1525-2027}, doi = {10.1029/2011GC003678}, pages = {15}, year = {2011}, abstract = {In the framework of the DEad SEa Rift Transect (DESERT) project a 150 km magnetotelluric profile consisting of 154 sites was carried out across the Dead Sea Transform. The resistivity model presented shows conductive structures in the western section of the study area terminating abruptly at the Arava Fault. For a more detailed analysis we performed a joint interpretation of the resistivity model with a P wave velocity model from a partially coincident seismic experiment. The technique used is a statistical correlation of resistivity and velocity values in parameter space. Regions of high probability of a coexisting pair of values for the two parameters are mapped back into the spatial domain, illustrating the geographical location of lithological classes. In this study, four regions of enhanced probability have been identified, and are remapped as four lithological classes. This technique confirms the Arava Fault marks the boundary of a highly conductive lithological class down to a depth of similar to 3 km. That the fault acts as an impermeable barrier to fluid flow is unusual for large fault zone, which often exhibit a fault zone characterized by high conductivity and low seismic velocity. At greater depths it is possible to resolve the Precambrian basement into two classes characterized by vastly different resistivity values but similar seismic velocities. The boundary between these classes is approximately coincident with the Al Quweira Fault, with higher resistivities observed east of the fault. This is interpreted as evidence for the original deformation along the DST originally taking place at the Al Quweira Fault, before being shifted to the Arava Fault.}, language = {en} } @article{QuesnelWeckmannRitteretal.2009, author = {Quesnel, Yoann and Weckmann, Ute and Ritter, Oliver and Stankiewicz, Jacek and Lesur, Vincent and Mandea, Mioara and Langlais, Benoit and Sotin, Christophe and Gald{\´e}ano, Armand}, title = {Simple models for the Beattie Magnetic Anomaly in South Africa}, issn = {0040-1951}, doi = {10.1016/j.tecto.2008.11.027}, year = {2009}, abstract = {The origin of the approximately 1000 km-long Beattie Magnetic Anomaly (BMA) in South Africa remains unclear and contentious. Key issues include the width, depth and magnetization of its source. In this study, we use uniformly magnetized spheres, prisms and cylinders to provide the simplest possible models which predict the 1 km-altitude aeromagnetic measurements along a profile across the BMA. The source parameters are adjusted by forward modeling. In case of a sphere, an inversion technique is applied to refine the parameters. Our results Suggest that two similarly magnetized and adjacent sources. With a vertical offset, can explain the observed magnetic anomaly. The best fitting model corresponds to two highly-magnetized (>5 A m(-1)) sheet-like prisms, extending from 9 to 12 kill depth, and from 13 to 18 kill depth, respectively, and with a total width reaching 80 km. Other less-preferred models show thicker and deeper magnetized volumes. Associated magnetizations seem to be mostly induced, although a weak remanent component is required to improve the fit. We also compare our results With the interpretation of independent magnetotelluric and seismic experiments along the same profile. It suggests that the geological sources for the BMA are mostly located in the middle crust and may be displaced by a shear zone or a fault. Contrary to previous models suggesting a serpentinized sliver of paleo-oceanic crust within the Natal-Namaqua Mobile Belt, we propose that granulite-facies mid-crustal rocks within this belt may cause the BMA.}, language = {en} }