Joint Modelling and Uncertainty Estimation for Site Characterization of Dhanbad City (India) Using Global Optimization.

We present a novel strategy for joint modelling to estimate shear wave velocities at ten sites in Dhanbad City, India. The joint modelling technique utilizes the complementary sensitivities of disparate datasets, such as horizontal-to-vertical spectral ratios (HVSR) and Rayleigh wave phase velocity dispersion curves, obtained from passive and active seismic surveys, respectively. The model search space is explored rigorously via the very fast simulated annealing (VFSA) global optimization technique and uncertainties are quantified with estimates of marginal posterior probability distributions (PPDs) and parameter correlation matrices (PCMs). These tools help us identify the portions of acceptable models that are well, or poorly, constrained. A confirmatory test is conducted to demonstrate the effectiveness of the modelling scheme by synthetic data as well as field data recorded in Dhanbad City. The depth to engineering bedrock is found to reach its maximum (~ 42 m) and minimum (~ 9.5 m) in the southwestern and northeastern parts of the city, respectively, while dominant frequencies range between 2 and 14.6 Hz. The largest Vs30 value found is 562 m/s at Dhanbad's southern border and 351 m/s in south-central neighbourhoods. Shear wave velocity profiles are consistent with borehole lithology data. The seismic characterization of Dhanbad City presented here will aid in seismic hazard mitigation efforts and facilitate infrastructure that can sustain the dynamic load imposed by earthquakes. [ABSTRACT FROM AUTHOR]