HR: 16:00h
AN: MR14A-01 INVITED     [Abstracts]
TI: Seismic discontinuities in the upper mantle
AU: * Kind, R
EM: kind@gfz-potsdam.de
AF: GFZ Potsdam, Telegrafenberg, Potsdam, 14473 Germany
AB: There are a number of seismological techniques which are able to see and to map discontinuities of physical parameters (density, velocity) in the upper mantle. Seismic tomography maps smooth parameter variations, not discontinuities. The best known technique are the receiver functions, which are rapidly developing since about ten years. Receiver functions are basically P-to-S or S-to-P converted waves at discontinuities. These are weak signals and they need summation of many seismic recordings and processing to become visible. These phases are much used to study the 410, 520 and 660 km discontinuities on a global scale, especially in subduction zones and near plumes. The topography of these discontinuities is thought to be a high resolution measure of in situ temperature. The crust-mantle boundary (Moho) is also well observed globally with receiver functions. Especially interesting is the subducted Moho and the possible effects of slab dehydration on the upper plate Moho. Reverberations within the crust often prevent usage of P receiver functions in the depth range between Moho and 410 discontinuity. These multiples however make it easy to determine absolute Moho depth and average crustal Vp/Vs on a much larger scale. S receiver functions have only very recently proven a good method to map the lithosphere-asthenosphere boundary (LAB). This boundary was so far rarely observed with high resolution body waves, mostly low resolution surface waves had been used. There are recent very detailed maps of the LAB near the Hawaii and Iceland plumes providing data for studies of plume-lithosphere interaction.
DE: 7200 SEISMOLOGY
DE: 7218 Lithosphere and upper mantle
SC: Mineral and Rock Physics [MR]
MN: 2004 AGU Fall Meeting