Wind-Induced Ground Motion: Dynamic Model and Nonuniform Structure for Ground

Wind-induced ground vibrations are a source of noise in seismic surveys. In a previous study, a wind-ground coupling theory was developed to predict the power spectral density of ground motions caused by wind perturbations on the ground surface. The prediction was developed using a superposition of the point source response of an elastic isotropic homogeneous medium deforming quasi-statically with the statistical description of the wind-induced pressure fluctuations on the ground. Model predictions and field measurements were in agreement for the normal component of the displacement but underpredicted the horizontal component. In this paper, two generalizations are investigated to see if they lead to increased horizontal displacement predictions: (1) First, the dynamic point source response is calculated and incorporated into the ground displacement calculation. Measured ground responses are used to incorporate losses into the dynamic calculation. (2) The quasi-static response function for three different types of nonuniform grounds are calculated and used in the seismic wind noise superposition. The dynamic point source response and the three more realistic ground models result in larger horizontal displacements for the point source at distances on the order of 1 m or greater from the source. However, the superposition to predict the seismic wind noise is dominated by the displacements very close to the point source where the prediction is unchanged. This research indicates that the modeling of the wind-induced pressure source distribution must be improved to predict the observed equivalency of the vertical and horizontal displacements.