Date of Award
M.S. in Physics
Physics and Astronomy
Wind noise is a problem in seismic surveys and can mask the seismic signals at low frequency. Development of practical solutions to this problem must be based on a good understanding of the mechanism of the wind-ground coupling. This thesis investigates the driving pressure and shear stress perturbations on the ground surface associated with wind-induced ground motions. A prediction of the ground displacements spectra from the measured ground properties and predicted pressure and shear stress at the ground surface is developed. Field measurements are conducted at a site in Marks, MS, having a flat terrain and low ambient seismic noise under windy conditions. Multiple triaxial geophones are deployed at different depths to study the wind-induced ground vibrations as a function of depth and wind velocity. Furthermore, a test experiment including a vertical and a horizontal mass-spring apparatus is designed to exert controlled normal pressure and shear stress to the ground. The match of the predictions and the measurements of the test experiment verify the linear elastic rheology and the quasi-static displacements assumptions of the model. Comparison of the predicted wind induced ground displacements spectra with the measured spectra shows good agreement for the vertical component but a significant underprediction for the horizontal componentss. The results indicate that the existing shear stress models significantly underestimate the wind shear stress at the ground surface and the amplitude of the fluctuation shear stress must be of the same order of magnitude of the normal pressure. This result might be useful for estimating ground surface shear stress under environmental flows in studies of soil erosion and sediment transport. Measurement results show that mounting the geophones flush with the ground provides a significant reduction in wind noise on all three components of the geophone. Further reduction in wind noise with depth is small for the depths up to 40 cm.
Naderyan, Vahid, "Wind Induced Ground Motion" (2015). Electronic Theses and Dissertations. 765.