Constraining the crustal composition of the continental US using seismic observables

The composition of the crust is one of the most uncertain and controversial com-ponents of continental estimates due to (1) limited direct access and (2) inconsistent indirect assessments. Here we show that by combining high-resolution shear velocity (Vs) models with newly measured with newly measured ratio of compressional wave veloc-ity (Vp) and Vs, or Vp/Vs ratio, for the crys-talline crust, a 3-D composition (SiO2 wt%) model of the continental crust can be derived with uncertainty estimates. Comparing the model with local xenolith data shows consis-tency at mid and lower crustal depths. The spatial patterns in bulk SiO2 content corre-late with major geological provinces, includ-ing the footprints of Cenozoic and Mesozoic mafic volcanism in the western U.S., and of fer new insight into the composition and evo-lution of the continental U.S.