Delineamento crosta continental-crosta oceânica através da magnetometria

We present a method to delineate the boundary separating the oceanic and continent crusts using magnetic data. The method maps magnetic lineaments, which happen to occur solely in the continental crust. To this end, the magnetic signal is amplified by downward continuing the magnetic anomaly to a surface defined by the bathymetry of the continental shelf, continental slope, and part of the continental rise. The purpose is to locate the seaward end of the lineaments. The downward continuation if formulated using the equivalent layer principle, leading to a large-scale system of linear equations, that was solved via a conjugate gradient method. To stabilize the solutions we used the first-order Tikhonov regularization functional (global smoothness constraint). Examples with synthetic data showed that, in contrast with the plain visual inspection of the original aeromagnetic data, which leads to an erroneous delineation of the boundary separating the oceanic and continent crusts, the continued magnetic anomaly delineates this boundary with excellent resolution. The method has also been applied to real aeromagnetic data from a Brazilian coastal area, evidencing that the data window is located above the continental shelf, or, possibly<br>above a transitional crust.