Inversion of gravity data from the Laguna Salada basin, B.C., Mexico

Abstract

A gravity interpretation of the Laguna Salada basin, B.C., Mexico is carried out by combining two inversion techniques for two-dimensional models. The ideal body theory is employed in combination with linear programming to compute bounds on the density contrast and thickness of the sedimentary fill at Laguna Salada. It is found that if a maximum density contrast of -0.3 g/cmJ is assigned to the model (based on geologic grounds), the structure can be no thinner than 3.7 km. These values provide a region of feasible solutions consistent with the gravity observations. These results are employed to introduce constraints on the calculation of the geometry of the anomalous source. The thin sheet approximation method is used to compute the initial model by a linear inversion method. This model is found to be within the bound obtained. Since this model does not fit satisfactorily the observed anomaly, an iterative procedure follows to calculate a model that minimizes the misfit between the observed data and its computed response. Seven iterations are necessary to reach a final solution. The sediments show it to be 5.3 km thick at its deepest point. Such a model is within the region of possible solutions and also consistent with the geological setting of the area.