Mapping Dispersion Misfit and Uncertainty in V_s Profiles to Variability in Site Response Estimates

摘要

Uncertainty in site response analyses can be attributed to a number of parameters, including analysis methods, input ground motions, nonlinear dynamic soil properties, and shear-wave velocity profiles. In this paper, several approaches commonly used to account for shear-wave velocity (V_s) uncertainty in site response are investigated. Specifically, the V_s profiles considered are categorized into three groups: (1) V_s profiles determined directly from surface-wave inversion, (2) simple statistical V_s profiles derived indirectly from the surface-wave V_s profiles (including bounding-type, median, and other percentile V_s profiles), and (3) statistically based, randomly generated V_s profiles. A companion paper discusses the development of these V_s profiles for two international blind-study sites. In this paper, the effects of using each approach to account for V_s uncertainty in site response are investigated by linking the dispersion misfit values for each V_s profile to variability in equivalent linear site response estimates. Clear trends exist between variability in site response estimates and dispersion misfit values at both sites. Thus, the experimental dispersion data can be used to help select suites of V_s profiles, generated either directly from inversion or through a randomization model, that account for uncertainty in a meaningful way without including unrealistic statistical profiles that result in too much site response variability.