Non-Stationary Random Field Simulation Method of Seabed Site Shear Wave Velocity Structures Considering Stratigraphy Variation and Nonlinear Trend
The spatial variabilities of stratigraphy and S-wave velocity(Vs)structures have significant influence on the results of seismic site response analyses.Based on the borehole data of the seabed of Bohai Bay,the embedded Markov chain model,which has a wider simulation range for random stratigraphy and smoother simulation effect for stratigraphic boundary than the coupled Markov chain,is used to simulate the variabilities of random stratigraphy with depth less than the borehole bottoms,and the simulation results have higher precision.The point estimation method is used to give the change of the means and standard deviations of Vs with h of the seabed when describing the variation trend of Vs with h by power function and linear function.Based on the measured Vs-profiles at the boreholes,the spatial variabilities of random Vs-structures are simulated by using the non-stationary conditional random field method.It is found that considering the spatial variabilities of the random stratigraphy and ignoring the nonlinear variation of Vs along h can significantly increase the standard deviations of the simulated random Vs-structures.The correlations and transfer probabilities between the unknown stratigraphy below the seabed borehole bottoms and the known stratigraphy at the same depth of near-shore land are established using the membership function and fuzzy Markov chain model,the possible spatial variabilities of random seabed stratigraphy and Vs-structures below the borehole bottoms are obtained.It provides reasonable random stratigraphy and Vs-structures for seismic response analysis of offshore engineering site.
seabed siteS-wave velocity structurespatial variabilitynon-stationary random fieldnonlinear trendearthquakesengineering geology
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