Fig. 5 Example FDD Peak Picking Plot for a Site in Richmond [3] 3.3 Processed Data and Map Generation Processed data, in the form of a spread sheet containing test name, coordinates and site period, was used to generate isoperiod maps of each test region, one for the North Shore and one for Richmond. This mapping was performed with the free software package Google Earth Toolbox [10] and Matlab. Site periods on the North Shore ranged from 0.04 to 1.25 seconds (0.8 to 25 Hz) as can be seen in Figures 6 and 7, and those in Richmond from 0.6 to 5.7 seconds (0.18 to 1.67 Hz) as can be seen in Figures 8 and 9. These results were expected, given the thick sediments of Richmond and the thinner sediments and exposed bedrock of the North Shore. Although accurate shear wave velocity was not available for this study, the “quarter wavelengths rule,” as seen in Equation 1, (1) (where P is the fundamental site period, Sv is average S wave velocity and d is the depth of the soil layer) can be used as a means of checking results [2]. It can be seen that shorter periods exist on the North Shore directly south of mountain ridges. This is consistent with expectations as the soil layer should be thinner when bedrock is closer to the surface and hence the period is shorter. Likewise, in Richmond longer periods are present where the coastline extends past that of the City of Vancouver‟s bedrock. Assuming this peninsula has been built up over time by sediment deposit, it is consistent with expectations that the period of this region would be longer. Fig. 6 Site Periods (in seconds) on the North Shore 456
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