Soil damping comes in two main forms: Belinostat damping (geometric dissipation of waves from spreading) or hysteretic material (also known as intrinsic) damping. Geometric dissipation is negligible for frequencies less than 1 Hz ,  and , and the majority of wind and wave loads have frequencies below 1 Hz (e.g. Refs.  and ). While the first and second fore-aft and side-to-side natural frequencies of the National Renewable Energy Laboratory 5 MW Reference Turbine (NREL 5 MW)  used in this paper are from 0.3 Hz to 3 Hz, the NREL 5 MW under extreme storm loading is dominated by first mode behavior. Because this first mode is at approximately 0.3 Hz, this paper neglects geometric dissipation and focuses solely on hysteretic material damping from soil. This type of soil damping should be more specifically labeled OWT monopile foundation damping (or generally referred to in this paper as “OWT foundation damping”) due to the specific formulation and mechanism of hysteretic material soil damping within the OWT soil-structure foundation system.