PhD thesis,

The structure of the southern Dead Sea basin revealed from local earthquake data

.
Freie Universität Berlin, (2011)

Abstract

While the Dead Sea basin has been studied for a long time, the available knowledge about the detailed seismicity distribution in the area, as well as the deeper structure of the basin, is limited. Therefore, within the framework of the international project DESIRE (Dead Sea Integrated Research Project), a temporary local seismological network was operated in the southern Dead Sea area. 65 stations registered 655 events within 18 month of observation time. A subset of 530 well locatable events were used to calculate a minimum 1-D model for P- and S-wave velocity. This minimum 1-D model served as an initial reference model for a vp and vp/vs tomography. Since the study area is at first order two-dimensional, a gradual approach was chosen, which compromised a 2-D inversion followed by a 3-D inversion. The sedimentary basin, clearly imaged through low P velocities and high vp/vs ratios, shows an asymmetric structure with a vertical eastern boundary and an inclined western boundary. The lower boundary of the basin, indicated by a large gradient of the P velocity, is found at 17 km depth. The boundary between fluid containing sediments, deposited during the formation of the basin, and pre-basin sediments is found between 10 and 15 km depth through contrasts in the vp/vs ratios. The Lisan salt diapir is furthermore imaged through low vp/vs ratios. Accurate earthquake locations are only revealed by tomographic inversions. The seismicity is concentrated in the upper crust down to 20 km depth while the lower limit of the seismicity is reached at 29 km depth. The seismic events at the eastern boundary fault in the southern part of the study area, represent the northwards transform motion of the Arabian plate along the Dead Sea Transform. North of the Boqeq fault the seismic activity, mostly related to the contrast between fluid containing sediments and 'dry' rocks, represent the transfer of the motion in the pull-apart basin from the eastern to the western boundary.

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