Crustal and upper mantle structure in the Amazon region (Brazil) determined with broadband mobile stations

[1] Three broadband stations operated from March 1997 to September 1998 in the Amazon region north of Manaus, Brazil, which, including the IRIS station PTGA (Pitinga), covered an area of roughly 60 × 200 km. Applying the receiver function technique to determine the crustal structure, there is evidence for an increase of the Moho depth from about 38 km below the Amazon Basin to approximately 48 km north of the basin. In addition, we analyzed the polarization of SKS-waves to determine anisotropy. The observed splitting parameters in a majority of the data set can be accounted for by a layer of axial symmetric anisotropy with the fast direction oriented roughly N110E. This direction cannot be associated with the present-day plate motion of the South American plate. However, the anisotropy may be related to a lithospheric fabric that was generated during the early tectonic history of the Amazonian Craton.

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