Geodynamic assessment of Eastern Mediterranean region: a joint gravity and seismic b value approach

Abstract

The Eastern Mediterranean region is tectonically complex, and its evolution is strongly related to the active subduction along the Hellenic arc which is the boundary between the African and the Anatolian-Aegean microplates. The overall tectonism of the region can be attributed to several events, such as the collision of African and Eurasian plates, convergence between Arabian and Eurasian plates and displacement of the Anatolian-Aegean microplate. The stress regime in Eastern Mediterranean region is a multi-component one. There are subduction zones governing the seismicity in the region, back arc events, and tension areas induced by the interference of continental and oceanic basins. This study has been achieved in order to evaluate this complex medium more discretely. The gravity changes in Crete and around Rhodes islands, which are located in the Mediterranean Sea, are influenced by more than one tectonic forces in Eastern Mediterranean Sea that are the continuity of each other especially in lateral direction with various rheological properties. Those changes were evaluated separately to understand the tectonic settlement of the area. For this purpose, the changes in the length of longwave of the Bouguer gravity data of both regions were determined by using two-dimensional upward analytical continuation technique. Later, in order to define the structural boundaries by tectonic movements and varying structural characteristic of the area, boundary analysis and vertical derivative methods were applied to these obtained Bouguer gravity values. In the second part of the study, seismicity belonging to both regions was examined. For this purpose, seismic b values of the study area were calculated in the form of moving windows and the obtained results were mapped. Finally, the amplitude change obtained from gravity studies, boundary analysis and vertical derivatives, and the maps regarding the b values and regional structures were evaluated together. It was determined that the results of boundary analysis and vertical derivatives both around Crete and Rhodes islands were consistent with the variation limits of b values.