Vibroacoustic predictions of sea-floor interface waves generated by offshore monopile installation

Pile driving for offshore monopile installation generates low-frequency ground vibrations that radiate outward along the sea–floor interface. These interface waves interact with surficial sediments, which exhibit elastic material properties. Near-field predictions of the vibroacoustic interactions that create these interface waves are generated by a 3-D Spectral Element Model (SEM) representing offshore pile driving of large, thin-walled cylindrical monopiles. Vibroacoustic predictions are coupled to a 2-D Parabolic Equation (PE) model that was adapted to include elastic wave equations to capture how vibrational energy will transmit between water and sediment layers. Realistic geoacoustic parameters are derived from underwater imagery and acoustic multibeam survey data, providing high-fidelity details about the surficial sediments in the vicinity of the monopile. The coupled models are used to investigate interface wave interactions across various surficial sediments and characterize interface wave propagation effects for the area. Comparisons of model predictions to measurements of ground vibration result in a better understanding of these waves and the potential to invert the acoustic properties of surficial sediments. Characterizing how interface wave effects influence the propagation of low frequency sound in water helps to improve predictions of the sound field generated by offshore monopile installation.