Various types of surveys can be taken depending on the thoroughness of the site characterization being sought. If only the overall vertical (depth) variation of stiffness information is needed, then a 1-D Vs profiling is sufficient (Fig. 1). If the lateral variation information is also important, a 2-D profiling can be conducted along a certain direction (Fig. 2). Considering that the minimum field operational cost for the 1-D profiling is usually more than half the cost for a 2-D profiling, a 2-D profiling is usually the recommended minimum approach. An anomaly—defined as a localized area significantly different in elastic property (strength and density) than ambient material— can be delineated through either 1-D or 2-D profiling if its size (dimension) is significant (for example, greater than 20% of its depth) (Fig. 3). Average and interval shear velocities are also provided as by-products for each 1-D or 2-D profiling survey (Fig. 4).
Fig. 1. Typical 1-D MASW survey and its 1-D shear-wave velocity (Vs) profile.
(Above) Fig. 2. Typical 2-D MASW survey and its 2-D shear-wave velocity (Vs) map. (Right) Fig. 3. Anomaly detection by 1-D (illustration) and 2-D (field data) surveys. (Below) Fig. 4. Display of average and interval shear-wave velocities at a site.