Dispersion analysis of surface wave testing - SASW vs. MASW

- The fundamental difference between the SASW and MASW was elucidated and clarified.
- Limitations and Pitfalls of 2-Station SASW were experimentally shown.
- A multi-shot common receiver survey method is proposed to replace SASW or substitute for conventional MASW.
- The common receiver configuration has better control of measurement range and higher lateral resolution.

The data reduction method for dispersion relation in surface wave testing is conventionally associated with the certain method of data acquisition, for example, phase shift analysis in the two-station SASW method and 2-D multi-station wavefield transformation of surface wave in the MASW method. The fundamental difference in dispersion analysis between the 2-station and multi-station approach was clarified in this study. Limited to the two channel data, conventional dispersion analysis of SASW suffers from possible phase un-wrapping errors, inefficient data filtering and synthesis, and inability to distinguish multiple modes. The MASW approach, on the other hand, can avoid these problems and provide visualization of dispersion relation through 2D wavefield transformation. As opposed to multiple shots in the SASW testing, the MASW testing typically uses only single shot, limiting the obtainable wavelengths due to near field and far field effects. Combining the merits of these two methods, a multi-shot common receiver configuration survey is proposed to acquire multi-station wavefield for 2D wavefield transformation using as few as two receivers. An additional benefit of the multi-shot common receiver configuration is shown to be better control and higher lateral resolution of the measurement range.