This project will involve the acquisition and analysis of seismic data from a network of broadband seismometers installed in Madagascar, the Comores Islands, and Mozambique in order to determine the origin of intraplate volcanism in the region. No modern seismic investigation of Madagascar, the world?s 4th largest island, has ever been made, and the source of the volcanism, not near any plate boundary, is unknown. This study seeks to determine if the volcanism is connected with either the giant lower mantle large low-shear velocity province (LLSVP) or with any of the upper mantle hot spots such as those beneath Afar or Reunion. The seismometers, borrowed from the IRIS PASSCAL pool of instruments, will be deployed in two installations: 18 in the summer of 2011 (in Madagascar, the Comores, and Mozambique), and 15 in the summer of 2012 (all in Madagascar). All seismometers will be retrieved in the summer of 2013. The broadband seismic data will be analyzed using several techniques in order to determine the sub-surface structure of the region. Both surface and body wave data will be use to generate 3D tomographic images of the crust and mantle; shear-wave splitting will be used to examine anisotropic fabric; P-to-S-wave conversions will be used to generate receiver functions for determining topography on the Moho and other sub-surface discontinuities.
The African LLSVP is the largest seismic anomaly within the earth; as an enormous thermochemical boundary layer between the mantle and core, it plays a vitally important role in controlling the nature of vertical mass flux within the mantle, and therefore of both mantle convection and its manifestation at the surface as plate tectonics. The African LLSVP is thought to play an important role in the abundant occurrence of hot spot volcanism on the African plate, but the mechanism by which this occurs is not known due to the extremely limited data sampling available at this location in the Southern Hemisphere. Further study of the sub-African LLSVP will be of interest to earth scientists in many disciplines, as will providing the first study of the sub-surface geology of Madagascar. This project will help in the training of U.S. graduate students as well as scientists in Madagascar and Mozambique, and will help strengthen the scientific ties between these three countries. This project will also be a scientific partner with AfricaArray, which has been a unifying positive force of science and good will in Africa.
This award is co-funded by NSF's Office of International Science and Engineering.
