Abstract Title: The Effects of Composition, Melting, and Temperature on the 
Seismic Velocity and Density of the Upper Mantle

Abstract Author(s): Schutt, Derek L. (University of Wyoming) - Lesher, C. E. 
(University of California, Davis)  

Abstract: A map of the temperature, degree of melting, and composition of the 
Great Basin upper mantle is an important step in understanding its evolution, 
flow, and geodynamics. With the wealth of data that will be collected by the 
USArray component of Earthscope, improved estimates of mantle P-wave and S-wave 
velocities will be available; however, these are only two observables to 
estimate (broadly) the three unknowns of temperature, melting, and composition. 
If mantle density structure can be estimated (for instance, through crustal 
uplift), this provides a third observable from which melting, temperature, and 
compositional variations can be more accurately determined. In many cases 
scaling relations between density and seismic velocity and temperature, 
melting, and composition, are estimated for olivine at standard temperature and 
pressure. We will present improved density scaling relations for temperature, 
melting, and compositional variations; and velocity scaling relations for 
temperature and compositional variations, for relistic upper mantle 
compositions, pressures, and temperatures. Among our findings are that density 
effects of temperature are often underestimated, and that melt depletion has no 
effect on the velocity of garnet peridotite.