COLLABORATIVE RESEARCH: A Global Study To Constrain The Amplitude of Short-Scale Length Topography on the 410 and 660km Discontinuities

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EAR-9909716Dueker The primary questions of this study will address are: what are the scale lengths of topography on the 410 and 660 km discontinuity? And how much does scattering induced by this topography bias estimates of the topography, amplitude, and sharpness of these discontinuities? Also, when topographic scattering is minimal, what are the details of the velocity profiles across the 410 and 660? As a pilot study, 46,000 radial and tangential receiver functions from the most data-rich global stations were made. To search for lateral variations, the converted S-wave piercing points at each station are binned into 40 km square patches at the 410 and 660, with only bins with more than twenty high quality receiver functions being studied. The effects of discontinuity topography scattering will be studied by analyzing the effects of varying the bin size and frequency content. Preliminary analyses indicate that up to 60 km of topography on the 410 and 660 km discontinuity can be found.