Small Strain Shear Modulus Derived From Offshore Seismic Reflection Data
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Small strain shear modulus Gmax is an important parameter for design of foundations of fixed offshore structures. The preferred reference method for Gmax is the seismic velocity test (SVT) performed as part of a seismic cone penetration test (SCPT). SVTs provide in-situ Gmax values for discrete depth sections of SCPTs. This paper focusses on added value achieved by (1) generation of 10 million synthetic Gmax profiles to 50 m depth and (2) a Gmax zonation map for the IJmuiden Ver Wind Farm Sites Alpha and Beta (offshore Netherlands). The synthetic Gmax profiles were derived from a data set of 58 actual SCPT profiles, 250 CPT profiles and 2D UHR seismic reflection traces along survey track lines spaced at about 70 m. The quality of the SCPT data and UHR seismic reflection data was state-of-the-art (as of 2021). The data process included the use of a (1) multi fidelity data fusion statistical framework and (2) machine learning by a convolutional neural network. The synthetic Gmax data were the basis for the Gmax zonation map used to enhance an integrated ground model for the wind farm sites. Particularly, the map can be used to quickly identify and constrain areas which are favourable and challenging for design of monopiles and other common foundation types typically considered for offshore wind turbines.