9614199 Wiens This grant provides $34,203 as one-half support of the costs of upgrading five workstations presently used by seismologists at Washington University. Specifically, their present SUN SS1, IPC and S10 will be upgraded with the SUN ULTRA 170 CPU, additional memory, SCSI internal hard disks and 20" color monitors. A variety of computationally intensive studies that are both interesting and fundamental problems in seismology and geophysics will utilize the capabilities of these upgraded workstations including, 3-D seismic tomography of subducted oceanic lithosphere beneath the Tonga trench, thermodynamic and seismic modeling of the Tonga slab using finite difference techniques and equations of state to locate possible depths of the olive-spinel phase transformation, studies of the distribution and frequency of aftershocks following the 1994 deep focus Tonga earthquake to look for clues as to the mechanisms behind deep-focus earthquakes (i.e. phase transformations, dehydration reactions), imaging of the structure of the core-mantle boundary through compressional wave mapping, imaging of the lateral and radial shear wave velocity structure of the lowermost mantle, generation of synthetic seismograms for visualization of seismic wave propagation through the Earth from crust to core and studies of the seismic velocity distribution in areas surrounding shallow faults. ***
