Abstract Title: Mapping mantle structure and fabric beneath the Basin and Range 
and surrounding regions

Abstract Author(s): Gaherty, James (LDEO) - Zhao, Li (USC) - LernerLam, Art 
(LDEO)  

Abstract: A principal goal of the EarthScope program is to develop a better 
understanding of the processes that control the assembly and evolution of the 
continents. Many of these processes are associated with upper-mantle structure 
and dynamics: mantle buoyancy drives surface deformation, for example, and 
variations in mantle strength control the extent, distribution, and character 
of the associated tectonism. Such processes are particularly active in the 
Basin and Range (B&R) and surrounding region, where the broad regional 
extension and high topography correlates with low-velocity (high-temperature) 
mantle. Seismic anisotropy provides an important tool for evaluating 
upper-mantle structure and dynamics because it can be directly related to past 
and present deformation, but improved observational techniques are required to 
characterize the distribution of anisotropy at regional scales in three 
dimensions. During the course of the EarthScope program, we hope to better 
constrain the dynamics of extension and tectonism by developing a 
regional-scale surface- and body-wave analysis to map seismic velocities and 
anisotropy and associated upper-mantle fabric beneath western North America. 
Using this model, we will evaluate the character of mantle fabric associated 
with a suite of tectonic processes in the B&R and adjoining regions. For 
example, what is the depth and spatial distribution of anisotropy beneath the 
central B&R, where shear-wave splitting patterns are complex? How does mantle 
fabric change across the transition from extension in the B&R to strike-slip 
along the San Andreas? At the workshop, we will present our ideas for 
addressing these questions.