3-D modeling Moho relief using gravity data: case in Red sea and Hellenic subduction zone
Reporter: Lo Yu-tsung
Abstract
• In this study, the forward and inversion method were used to evaluate the Moho relief in two regions. In Red sea area, 3-D gravity data have been used in addition to continental and marine seismic profiles, well logs and geological cross-sections. The gravity data has improved the geometry and the density distribution in the 3-D calculated profiles. Results of the current work reveal possible crustal thickness and density distribution between the sedimentary cover and the upper mantle including the Moho discontinuity. The Moho depth map of the region, as obtained from the 3-D modeling exhibits various crustal thickness distributions. The type of crust changes gradually from continental to oceanic, from north to south. Using inversion method in the Red sea and Hellenic, the main goal of our study is to investigate 3D topography of the Moho boundary for the area. For potential field data inversion we apply a new method of local corrections. The method is efficient and does not require trial-and-error forward modeling. To separate sources of gravity field in depth, a method is suggested, based on upward and downward continuation. Both new methods are applied to isolate the contribution of the Moho interface to the total field and to find its 3D topography. At the first stage, we separate near-surface and deeper sources. According to the obtained field of shallow sources a model of the horizontal layer is suggested, which includes a density interface between light sediments and crystalline basement. Its depressions and uplifts correspond to known geological structures. At the next stage, we isolate the effect of very deep sources (below 100 km) and sources outside the area of investigation. After subtracting this field from the total effect of deeper sources, we obtain the contribution of the Moho interface. The gravity model approach using two different methods in two regions always solves the Moho relief, and the result is consistent with the geological and tectonic interpretation of previous studies.
References
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