Description: Magnetotelluric and seismic methods provide complementary information about the resistivity and velocity structure of the subsurface on similar scales and resolutions. No global relation, however, exists between these parameters, and correlations are often valid for only a limited target area. Independently derived inverse models from these methods can be combined using a classification approach to map geologic structure. The method employed is based solely on the statistical correlation of physical properties in a joint parameter space and is independent of theoretical or empirical relations linking electrical and seismic parameters. Regions of high correlation (classes) between resistivity and velocity can in turn be mapped back and reexamined in depth section. The spatial distribution of these classes, and the boundaries between them, provide structural information not evident in the individual models. This method is applied to a 10 km long profile crossing the Dead Sea Transform in Jordan. Several prominent classes are identified with specific lithologies in accordance with local geology. An abrupt change in lithology across the fault, together with vertical uplift of the basement suggest the fault is sub-vertical within the upper crust.

Description: Tomographic inversion techniques were applied to first-arrival traveltimes of refracted P waves to study the shallowest part of the crust in the vicinity of the Arava Fault (AF), the Dead Sea Transform (DST) segment between the Dead Sea and the Red Sea; tomographic inversion techniques were applied to first-arrival traveltimes of refracted P waves. A 100-km-long seismic line was centered on and oriented approximately perpendicular to the AF. A large number of P wave traveltimes from vibroseis and explosive shots (〉 280,000) were picked manually and used to invert for shallow P wave velocity structure. The regularized inversion approach (Zelt and Barton, 1998) was used for the tomographic inversion of the traveltimes. Extensive testing of model and inversion parameters was carried out to derive a reliable P wave velocity model. Complementary checker-board tests indicate that depending on the size of velocity homogeneities, the velocity structure is well resolved down to a depth of several kilometers. This model represents the first shallow P wave velocity across the whole width of the DST system, showing features that correlate well with surface geology and also some buried structures. The model further suggests that the AF extends vertically downward to at least 3 km. The observed variation in upper-crustal velocity implies the existence of a simple deformation compatible with a large lateral fault offset. From this model, a structural and dynamic interpretation of the DST system is then presented. The depth extension and geometry of several additional major faults and DST-associated shallow sedimentary basins were successfully imaged through the integration of the well-known surface geology and nearby boreholes. This work again confirms the DST as a typical transform fault system with a dominant strike-slip motion confined to a narrow zone.

Description: This volume contains the results of the DESERT project running from 2000 to 2006. It opens with a review paper (DESERT Group, 2009) followed by 33 special papers, see list of content (529 pages).

Description: Fault zones are the locations where motion of tectonic plates, often associated with earthquakes, is accommodated. Despite a rapid increase in the understanding of faults in the last decades, our knowledge of their geometry, petrophysical properties, and controlling processes remains incomplete. The central questions addressed here in our study of the Dead Sea Transform (DST) in the Middle East are as follows: (1) What are the structure and kinematics of a large fault zone? (2) What controls its structure and kinematics? (3) How does the DST compare to other plate boundary fault zones? The DST has accommodated a total of 105 km of left‐lateral transform motion between the African and Arabian plates since early Miocene (∼20 Ma). The DST segment between the Dead Sea and the Red Sea, called the Arava/Araba Fault (AF), is studied here using a multidisciplinary and multiscale approach from the μm to the plate tectonic scale. We observe that under the DST a narrow, subvertical zone cuts through crust and lithosphere. First, from west to east the crustal thickness increases smoothly from 26 to 39 km, and a subhorizontal lower crustal reflector is detected east of the AF. Second, several faults exist in the upper crust in a 40 km wide zone centered on the AF, but none have kilometer‐size zones of decreased seismic velocities or zones of high electrical conductivities in the upper crust expected for large damage zones. Third, the AF is the main branch of the DST system, even though it has accommodated only a part (up to 60 km) of the overall 105 km of sinistral plate motion. Fourth, the AF acts as a barrier to fluids to a depth of 4 km, and the lithology changes abruptly across it. Fifth, in the top few hundred meters of the AF a locally transpressional regime is observed in a 100–300 m wide zone of deformed and displaced material, bordered by subparallel faults forming a positive flower structure. Other segments of the AF have a transtensional character with small pull‐aparts along them. The damage zones of the individual faults are only 5–20 m wide at this depth range. Sixth, two areas on the AF show mesoscale to microscale faulting and veining in limestone sequences with faulting depths between 2 and 5 km. Seventh, fluids in the AF are carried downward into the fault zone. Only a minor fraction of fluids is derived from ascending hydrothermal fluids. However, we found that on the kilometer scale the AF does not act as an important fluid conduit. Most of these findings are corroborated using thermomechanical modeling where shear deformation in the upper crust is localized in one or two major faults; at larger depth, shear deformation occurs in a 20–40 km wide zone with a mechanically weak decoupling zone extending subvertically through the entire lithosphere.