UCLA

The shear-wave velocity profile database was augmented with 259 profiles from 205 unique sites in Utah to facilitate the assignment of site parameters for 95 ground motion recording sites in this region as part of the NGA-West3 project. Three profiles were paired with Utah ground motion stations but 92 other stations lack a co-located profile. A proxy-based model to predict the time-averaged velocity in the upper 30 m of the site (VS30) was developed that considers surface geology and surface gradient for Quaternary units in Utah. The Quaternary surface geologic units considered are Holocene alluvium (Ha), fill (Hf), Pleistocene or undifferentiated Quaternary alluvium (Pa/Qal), alluvium/deltaic (Pad), deltaic (Pd), deltaic-lacustrine or lacustrine (Pdl/Pl), glacial (Pg), undifferentiated Quaternary alluvium - deltaic - eolian (Qa/Qdel/Qe), undifferentiated Quaternary alluvium/deltatic/lacustrine and Holocene deltaic/lacustrine (Qalm/Qdl/Hdl), and lacustrine (Ql). For each unit, VS30-dependence on surface gradient, computed from a digital elevation model with 30 arc-sec resolution, was evaluated and gradient dependencies were identified for 5 of the 11 quaternary units (generally those of Holocene age). The available profile data did not allow the development of models for rock sites, for which VS30 was estimated using geology-based models developed for other regions.