Analysis and Interpretation of the Texas A&M University Benchmark Data Using the Refraction Microtremor Technique

We applied the refraction microtremor (ReMi) technique (Louie, 2001) to determine the shear-wave velocity structure from benchmark data collected at the National Geotechnical Experimentation Site (NGSE) at Texas A&M University. Three data sets were evaluated: the active Multichannel Analysis of Surface Waves (MASW) data at Site 98 and Site 122, which were recorded by 62 receivers at 2 ft spacing and the passive MASW data, which were recorded by 32 receivers at 10 ft spacing. The essence of the ReMi technique is the separation of Rayleigh waves from other wave arrivals using a two-dimensional slowness-frequency transform of the seismic records. We use a new method introduced by Pancha et al. (2008) to image and evaluate the dispersion curve envelope via power-slowness profiles through the slowness-frequency plots. These images demonstrate the appropriateness of our phase picks used to invert for velocity structure beneath the test site locations.