The Keel of the Amazonian Craton

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This project aims to reveal lateral and vertical variations within the lithospheric keel of Precambrian South America through imaging the S-velocity structure of the upper mantle and crust beneath northern South America. This imaging will be based on a combination of seismic data from the BLSP02 network with pre-existing data.The BLSP02 network represents a completed field experiment, which was a joint effort between the University of Sao Paulo and the Swiss Federal Institute of Technology. The BLSP02 experiment gathered seismic data on about fifteen broadband seismometers in the period 2002-2004. The seismometers were placed throughout all of eastern Brazil.Variations within Precambrian keels provide clues to their formation and evolution. Further constraints on their formation and evolution comes from the proposed comparison with the keel of Precambrian North America, which is extensively studied separately and in the past. Imaging such variations is done through seismic tomography. The tomographic method to be applied combines measured surface wave group velocities with regional waveforms, independent estimates of crustal thickness, and arrival times of teleseismic S waves. The combination of these different types of data optimally enhances resolving power for lateral and vertical variations in seismic rigidity within the large region that encompasses Precambrian South America.This research is being jointly funded by the Geophysics program and the Office of International Science and Engineering, which is supporting the collaboration between the US and Brazilian scientists.