Kinematic modelling of large-scale structural asymmetry across the Dead Sea Rift

Abstract

The Dead Sea Rift (DSR) is characterized by large-scale topographic and structural asymmetries: the rift's eastern side is flexed upward toward the axis and its overall shape resembles an uplifted shoulder; the western side of the rift is flexed down toward the axis and its overall shape resembles a wide arch. We use a kinematic model of the lithosphere to explain the cumulative deformation of the pre-rift topography in response to two tectonic processes: normal faulting due to lithospheric extension and isostatic uplift. The model considers the sum relief of three surfaces: relief that existed prior to the formation of the rift (initial topography), relief created by slip along a curved normal boundary fault (kinematic topography), and relief created by isostatic response of the lithosphere to this faulting and to an additional unmodelled load (isostatic topography). The model predicts the observed structure across the rift only when we considered a significant additional load, comparable in magnitude to the load induced by the kinematic topography. The additional load reflects the negative mass anomaly of the 8–10-km-deep Dead Sea Basin, which is filled with unconsolidated sediments. By constraining the model with the structural observations, we determined that the extension perpendicular to the rift axis lies in the range 1–4 km in the northern half of the rift and 2–8 km in the southern half. The model also explains other observations across the DSR, such as the configuration of the three present-day regional drainage systems and the observed low-magnitude upward deflection of the Moho beneath the rift.