Using mechanical modeling to constrain fault geometries proposed for the northern Marmara Sea

摘要

In recognition of potential seismic hazard along the North Anatolian fault within the Marmara Sea, geophysical surveys have recently been conducted to collect high-resolution bathymetry and seismic reflection data. Despite the high quality of the data, fault interpretations by different authors are varied and a conclusive fault geometry within the Marmara Sea remains elusive. This paper presents a mechanical modeling method for constraining proposed fault geometry interpretations. In the model, crustal faults within the Marmara Sea slip in accordance with GPS-constrained slip rates along deep plate boundary dislocations. We test three fault models proposed by others and show that an interpretation with a series of pull-apart basins along a master strike-slip fault best produces the observed deformation pattern within the Marmara Sea. The locations and relative subsidence of the basins along the northern Marmara trough are well matched. The computed slip vectors on the faults in the best fitting model indicate that, except for small faults bounding the Tekirda? basin, the faults have dominantly right-lateral slip, with rakes within 15° of horizontal. On the local scale, this suggests that interaction between the segmented strike-slip faults is the dominant mechanism producing the observed vertical deformation in the Marmara Sea. On the regional scale, if the Marmara Sea faults behaved in this manner over geologic timescales, then right-lateral plate boundary motion, without an additional component of north-south extension associated with the Aegean Sea, is sufficient to produce the Marmara Sea pull-apart basin morphology.