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P-AND S-WAVE 3D VELOCITY MODELS FOR THE SOUTH AMERICAN PLATFORM

Abstract:

With the installation and growth of the Brazilian Seismographic Network (RSBR) since 2011, it is now possible to detect and locate events with magnitudes lower than 3.5 mb for Brazil, and better study the local and regional seismicity. Nevertheless, most of these events are located using 1D velocity models that lead to larger uncertainties precluding any correlation with the known geological structures. The use of heterogeneous 3D velocity models better pbkp_redicts the travel times and guarantees the accuracy of hypocenter location; however, there is not yet a calibrated 3D velocity model for the South American Platform (SAP). In this study, integrating multiple local and regional geological and geophysical knowledge and average velocities of the crust and mantle, we have elaborated 3D P-and S-wave velocity models for the SAP, including the Central Andes area (down to 900 km). We tested the model locating the well-known 1998 Andean Aiquile earthquake (Bolivia), 6.6 Mw, obtaining successful results when compared with its ground truth location. We also satisfactorily located two other recent important events of the SAP, using local and regional body wave arrivals recorded by the RSBR. Finally, S-wave arrivals of near stations helped to constrain the event depths to expected values.