HR: 17:00h
AN: S52J-05    [PDF]
TI: Structure of the Lithospheric Keel Beneath the Tanzania Craton From the Joint Inversion of Receiver Functions and Surface-Wave Dispersion
AU: * Julia, J
EM: jjulia@geosc.psu.edu
AF: The Pennsylvania State University, Department of Geosciences Deike Bldg., University Park, PA 16801 United States
AU: Ammon, C J
EM: cammon@geosc.psu.edu
AF: The Pennsylvania State University, Department of Geosciences Deike Bldg., University Park, PA 16801 United States
AB: The Tanzania Craton is a segment of old continental lithosphere that sits in the midst of the southward-propagating East African Rift System. This is a unique tectonic setting in which the lithospheric keel underlying the craton may be in contact with hot mantle material, and interesting questions regarding cratonic stability (such as the degree of erosion or disruption of the keel by the upwelling mantle) remain. In this study, we present S-wave velocity models beneath the 1994-95 Tanzania Passive-Source Seismic Experiment stations, which covered much of the craton and parts of the surrounding mobile belts. The models have been obtained by combining receiver functions and fundamental mode surface-wave dispersion velocities in a joint inversion for subsurface velocity structure. The combination bridges resolution gaps among the data sets and provides better constrained images of the subsurface than either of the individual data sets alone. Preliminary inversion results show the presence of a prominent low velocity zone (LVZ) at 150-200 km depth when sampling subsurface structure in an EW direction, suggesting disruption of the continental lithosphere. When the subsurface is sampled in a NE-SW direction, however, the LVZ disappears and a high-velocity sub-craton lithosphere is observed, suggesting that the craton is underlain by an undisrupted lithospheric keel. The observed azimuthal differences in deep structure may be reconciled by the incorporation of 3D effects in the base of the lithosphere or anisotropy across the base of the lithosphere, perhaps providing clues to present or fossil flow in the region.
DE: 7205 Continental crust (1242)
DE: 7218 Lithosphere and upper mantle
DE: 8150 Plate boundary--general (3040)
SC: Seismology [S]
MN: 2003 Fall Meeting