Stress field fluctuations along the Dead Sea rift since the middle Miocene

The Dead Sea transform (DST) is the suture between the African and the Arabian plates, both of which subduct northward under the Eurasian plate. The collision of these plates with Eurasia and their relative motion are the source for their internal deformation, especially in the vicinity of the Dead Sea transform. Geological observations indicate that two distinct paleostrain regimes operated adjacent to the Dead Sea rift and in the Sinai-Israel subplate: (1) WNW shortening (less than 10%) and NNE extension, beginning in the Turonian, is associated with the development of the Syrian Are fold belt and attributed to the Syrian Are stress field (SAS); and (2) middle Miocene to Recent NNW shortening and ENE extension, associated with the 105-km sinistral displacement along the Dead Sea transform and the opening of the Red Sea, is attributed to the Dead Sea stress field (DSS). It was originally suggested that the SAS terminated during the middle Miocene with initiation of the DSS. However, trend and age analysis of many structures shows that formation of SAS-compatible structures continued after the middle Miocene up to the Recent. In some middle Miocene and younger rocks structures, such as faults, dikes, volcanic lineaments, and tectonic stylolites compatible with both stress fields were reported. In a few locations, structures compatible with both stress fields crosscut each other. It is suggested that the movements which resulted in the development of the Syrian Are and other SAS-compatible structures are continuing to the Recent and that DSS movements are superimposed upon them. The overlapping of SAS and DSS structures adjacent to the DST results from spatial and temporal fluctuations in the overall stress state. We propose that such variations could be caused by the superposition of large earthquake stress drops, associated with movements along the DST, on a steady background, plate scale, stress regime associated with the SAS. Thus DSS-compatible structures should form in preseismic activity periods, when DST-related elastic strain is high. On the other hand, the SAS-compatible structures should form during interseismic activity times, subsequent to large local stress release along the DST.