Upper crustal structure of the eastern Basin and Range, northern Colorado Plateau, and Middle Rocky Mountains from Rayleigh-wave dispersion

Short-period (4 to 22 sec) Rayleigh waves generated by nuclear blasts at NTS and Rio Blanco were analyzed digitally to obtain group-velocity dispersion curves. These data were used to determine upper crustal structure for the eastern Basin and Range, northern Colorado Plateau, and Middle Rocky Mountains provinces. The crustal models obtained were in good agreement with refraction results. In the eastern Basin and Range, generally low S-wave velocities and an upper crustal low-velocity layer (LVL) were indicated, but there was no evidence for a LVL in the other provinces.