Practical Focusing of Surface-Wave Inversion to Image Levees in Southern New Mexico

Existing algorithms for inversion of dispersion-curves estimated from analyzing the seismic surface-wave data provide a reasonable representation of the overall shear-wave velocity structure. However, in some cases these results may not meet the resolution requirement of the survey objectives targeting the upper portion of the subsurface section. Near-surface geophysical surveys often look for greater detail in the very near surface, such as the case for levees, while still being interested in the overall velocity structure at greater depth. The proposed method for applying surface-wave inversion revolves around applying a greater degree of focusing on the very near-surface component of the inversion model through the practical use of existing algorithms. Specifically by eliminating the low frequency portion of the dispersion-curve data and using a shallower model. The proposed inversion technique is demonstrated using the multi-channel analysis of surface waves (MASW) inversion algorithm. As a result of using this near-surface focusing approach, surface-wave velocity estimates of the levees possess greater detail and resolution. Results presented here demonstrate the potential of the proposed approach to more accurately image the very shallow subsurface top portion of other near surface MASW sites.