  This article extends a recently proposed heterogeneous data assimilation
technique for site characterization to estimate compression and shear wave
velocity (Vp and Vs, respectively) and damping at Treasure Island and Delaney
Park downhole arrays. The adopted method is based on the joint inversion of
earthquake acceleration time series and experimental surface wave dispersion
data, and including physical constraints to improve the inverse problem's
well-posedness. We first use synthetic data at these two sites to refine the
proposed approach and then apply the refined algorithm to real data sets
available at the Treasure Island and Delaney Park downhole arrays. The joint
inversion results show that the estimated Vs and Vp profiles are in very good
agreement with measured profiles at these two sites. Our synthetic and real
data experiment results suggest that Vp estimation from inversion at downhole
arrays can be improved by integrating the water table depth information or the
higher modes of the Rayleigh wave dispersion data. Depending on the site
complexity, water table information can also help reduce uncertainties
associated with damping estimation. In the last part of this article, we
compare the performance of the inverted profiles to other methods used to
incorporate spatial variability and wave scattering effects in 1D ground
response analysis (GRA). The comparisons show that the joint inversion-based Vs
and Vp profiles and damping ratios estimated in this article can effectively
integrate the effects of spatial variability and wave scattering into 1D GRAs,
especially at the Delaney Park downhole array, which is classified as a poorly
modeled site using traditional 1D GRA.
