Measurement uncertainty of shear wave velocity: A case study of thirteen alluvium test sites in Taipei Basin

Field seismic methods are widely applied to site investigations for seismic design. The most often used ones are cross-hole, down-hole, SCPT, suspension P–S logging, and surface wave methods. The choice of seismic methods has a variety of technical and cost considerations. However, the measurement uncertainty among resulting shear wave velocities by above methods are rarely statistically characterized with mathematical models and sound database in the literature, even though it is an important factor to consider before choosing a method. In this study, thirteen alluvium sites in Taipei Basin were chosen and carefully planned to simultaneously measure the velocity profiles using each of the five most common seismic methods with conventional shear wave triggering techniques. Using the data from the test and statistical models, the differences between seismic methods were quantified as the calibrated measurement uncertainty, which can be used as a reference for selecting an appropriate method for measuring shear wave velocity. Finally, the effect of measurement uncertainty on seismic site classification and simplified soil liquefaction potential evaluations based on shear wave velocity was investigated.