SHEAR WAVE SPLITTING AND UPPER MANTLE ANISOTROPY BENEATH SOUTHERN NEW ENGLAND

The geological structure of southern New England is complex, reflecting a host of past tectonic processes including subduction, terrane accretion, and rifting. The structure of the crust and upper mantle beneath the region is also presumably complex, but it is harder to study because of its inaccessibility. Seismic anisotropy, or the directional dependence of seismic wave speeds, is a result of (past or present) mantle deformation, and measurements of seismic anisotropy thus yields constraints on the deformation of the mantle lithosphere due to past tectonic processes. Here we examine SKS splitting patterns for a set of 15 long-running broadband seismic stations in New York, Connecticut, Massachusetts, and Rhode Island, in order to understand patters of seismic anisotropy beneath southern New England. We measure the splitting of SKS phases over a range of backazimuths and examine the variability of apparent splitting patterns with backazimuth. We find evidence for complex and laterally varying anisotropy beneath southern New England, reflecting complicated patterns of deformation in the past.