3D KINEMATIC INVERSION FROM A SET OF LINE PROFILES1

In the case of 3D multilayered structures the 2D interval velocity analysis may be inaccurate. This fact is illustrated by synthetic examples. The method proposed solves the 3D inverse problem within the scope of the ray approach. The solution, i.e. the interval velocities and the reflection interface position, is obtained using data from conventional 2D line profiles arbitrarily located and from normal incidence time maps. Although the input information is essentially limited, the method presented reveals only minor biased velocity estimates. In order to implement the proposed 3D inversion method, we developed a processing procedure. The procedure performs the evaluation of reflection time and ray parameters along line profiles, 3D interval velocity estimation, and time-to-depth map migration. Tools to stabilize the 3D inversion are investigated. The application of the 3D inversion technique to synthetic and real data is compared with results of the 2D inversion.     

Late Neogene rift valley fill sediments preserved in caves of the Dead Sea Fault Escarpment (Israel): palaeogeographic and morphotectonic implications

Evaporitic‐lagoonal marl and dolomite laminar fill sediments are preserved in relict dry caves of the Dead Sea Fault Escarpment (Israel) which has been tectonically active since the Late Neogene. The hosting caves are located within Turonian massive carbonate bedrock and at higher altitudes than previously documented fill sediments of the Dead Sea depression. Based on the relative altitudes of the cave sediments, the ‘reversed stratigraphy’ of the Dead Sea depression fill sediments, possible partial correlation of the cave sediments with other fill sedimentary units of the depression, and sedimentary, geochemical and mineralogical characteristics, it is concluded that: (i) the cave sediments are among the oldest of the depression fill; and (ii) the deposition of the cave sediments took place in hypersaline dolomite‐precipitating water bodies of Late Neogene age, during the initial morphotectonic stages of the depression formation. Variable and relatively low Sr/Ca and δ³⁴S ratios of the cave sediments (assuming precipitation from sea water) suggest variable fresh water input into the depositional brine. The present altitudes of the cave sediments reflect Late Neogene levels of water bodies in the depression, modified by vertical post‐Late Neogene tectonic movements within the still active fault escarpment. According to these altitudes, a 50 to 250 m uplift of the western margins of the depression since the Late Miocene to Early Pliocene is inferred.