Seismic heterogeneities beneath the Atlantic and Africa - thermal or chemical?

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We are planning to investigate seismic structures in the Earth s mantle beneath the South Atlantic and Africa, associated with the large low velocity shear wave anomaly that can be seen in tomographic images. Using array seismology and migration and extracting as much information as possible from the seismic wavefield, we will try to determine, whether the large shear wave anomaly has a thermal or chemical origin. Events in South America and South Sandwich Islands recorded at permanent and temporary arrays in Africa will especially illuminate the edge of the large shear velocity anomaly beneath the South Atlantic. Searching for seismic structures and using differential structures (one event gives information on structures in several depths) and information on waveforms, frequencies etc, we can determine the extent of the anomaly and the physical parameters of the observed seismic structures. Seismic modeling results with inputs from geodynamic studies and mineral physical parameters will be compared to the observed seismic data after analysing the synthetic data in the same way as the observations. Using all information, we can test the different hypotheses regarding the origin of the anomaly.