DYNAMIC STRENGTH EXPERIMENTS THROUGH A BLOCK MODELING APPROACH FOR THE EASTERN MEDITERRANEAN REGION

Abstract:

The concept of long-term lithological strength and its spatial variations is an issue of much debate. Despite huge efforts, a consensus among researchers remains elusive. Part of the reason for this is that continuously varying strength is an impossible scenario in block models which only allow spatially non-varying strain rates within individual blocks. However, it is possible to impose and/or invert for variable coupling coefficients along mapped block boundaries. Such coupling coefficients can either come from direct observations of strength such as boreholes or from dynamic models that fit geodetic fields provided by GPS and/or INSAR observations. The tectonically active Eastern Mediterranean region poses important hazard-related questions such as the state of coupling along the Hellenic trench and deformation along the Cyprus arc are directly linked to the lateral strength distibution of the deforming areas to the north. In this study we explore two distinct block architectures for the eastern Mediterranean region: a complex block configuration as suggested by previous GPS studies with optimized block architecture (to best fit the geodetic velocity field) and another simple configuration based on a recent geological study that delineated blocks using geological features such as demarcated ophiolitic zones, known highly strained ductile shear zones etc. We then run a series of dynamical strength inversions assuming several different values of the ratios for the long-term pore-pressure to the lithostatic pressure and brittle-ductile transition depth. For each case we run checkerboard tests and finally analyze the ramifications in terms of the spatial distribution of the misfits and the state of coupling along the Hellenic Trench and Cyprus arcs.