The first step in modeling the sediment basement depth through available Bouguer anomalies is to remove the gravity effect of the Moho relief. This effect is computed by discretizing the model space between the ground surface and Moho discontinuity. TO compute the gravity effect of model space, the quad tree mesh is applied to mesh the ground surface. Then the depth of the center of each cell of quad tree mesh to the Moho is interpolated. The gravity effect of each cell that is now actually a rectangular prism is compute through relevant equation. At last the gravity effects of all these rectangular prisms represent the gravity effect of the model space. Subtracting the gravity effect of the model space from Bouguer anomalies, the Moho-free Bouguer anomalies are obtained.

The relief of the basement in the survey area is estimated by inverting the Moho-free Bouguer anomalies through the least-square minimization method that is available through a python library which is called Scipy.

Our modeling results indicate an only 100 kg/m3 density contrast between the crust and the upper mantle is sufficient to provide a basement depth. This is interpreted as high density and mafic affinity of the lower crust beneath the Zagros collision zone due to the eclogite in its deep part. Alternatively, the cratonic core of Zagros keel has a small density leading to only a 100 kg/m3 density contrast between the lower crust and the uppermost lithospheric mantle.