EARTH <br />DYNAMICS <br />LLC <br /> <br />ReMi Analysis 1200 Alder St <br />October, 2025 <br /> <br />Page 2 <br /> <br /> <br />Data reduction is completed in two steps. First, the time versus amplitude seismic <br />records are transformed into spectral energy shear wave frequency versus shear wave <br />velocity (or slowness). The data are graphically presented in what is commonly termed <br />a p-f plot. The interpreter determines a dispersion curve from the p-f plot by selecting <br />the lower bound of the spectral energy shear wave velocity versus frequency trend. <br />The second phase of the analysis consists of fitting the measured dispersion curve with <br />a theoretical dispersion curve that is based upon a model of multiple layers with various <br />shear wave velocities. The model velocities and layer thicknesses are adjusted until a <br />‘best fit’ to the measured data is obtained. This type of interpretation does not provide a <br />unique model. Interpreter experience and knowledge of the existing geology is <br />important to provide a realistic solution. The data are presented as one-dimensional <br />velocity profiles that represent the average shear wave velocities of the subsurface <br />layers over the length of the geophone array. <br /> <br />For this project, data were acquired along one ReMi array consisting of twenty-four 4.5 <br />Hz vertical geophones spiked in firm soil with a geophone spacing of thirteen feet and a <br />total array length of 299 feet. More than thirty 30-second-long seismic records of <br />ambient seismic noise were recorded for each array. Data were acquired when <br />vehicles, and people were moving on and near the site. <br /> <br /> <br />4.0 RESULTS <br /> <br />The approximate location of the ReMi array is shown on the Google Earth image in <br />Figure 4-1. The ReMi analysis and results for ReMi Array 1 are contained in Figure 4-2. <br />Figure 4-2 includes the p-f plot, the dispersion curve, the derived velocity versus depth <br />model that best fits the data and expected geology of the site and a table containing the <br />shear wave velocity with depth for the array. <br /> <br />The dispersion curve is well developed and distinct. The RMS error of the model fit to <br />the data is less than 25 ft/s. The dispersion curve data suggest that the depth of <br />investigation for this project is at least 100 feet bgs. <br /> <br />