Three-Dimensional Shallow Shear-Wave Velocity Model for the Las Vegas Valley

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A three-dimensional (3-D) shear-wave velocity (Vs) model was developed for the heterogeneous sediments of the Las Vegas Valley (LVV) in Nevada. The model was based on more than 200 Vs profiles (one-dimensional representation of Vs versus depth) and 1,400 geologic well logs. Incorporation of the well logs into the model was accomplished by condensing the geologic-log descriptions of the shallow sediments into five sediment units then correlating Vs to these units. Characteristic Vs profiles were defined to represent four of these units by correlating between closely spaced pairs of Vs measurement sites and wells located within 500 m. These characteristic profiles were then used to generate Vs profiles at each well location by assigning Vs based on logged sediment type with respect to depth. The fifth unit was cemented sediment, for which a constant, depth-independent Vs value was assigned. Using the software EarthVision, the Vs profiles were interpolated in three dimensions, considering faults, to nearly 400 m in depth. Using regional data from an existing gravity-based survey, the model was to extend to Paleozoic bedrock, which is locally deeper than 4 km. A 3-D section of the model demonstrated strong variability of Vs both laterally and vertically. Model accuracy varied spatially with data density. This model can be used to forecast earthquake ground-shaking patterns throughout the LVV. Particular application in engineering seismology can be found for high-rise structures that are vulnerable to long-period ground motion in a deep sedimentary basin.


Civil and Environmental Engineering | Engineering | Environmental Engineering | Geophysics and Seismology


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