SEGJ Technical Conference

Practical Applications of Hybrid Surface Wave Method Combining MASW and LAMS for Earthen Levee Investigations

Abstract The authors had reported that LAMS (Linear Array Microtremor Survey Method) is an advanced technique to be used at high-levees to obtain S-wave velocity structures from the levee crown to its substrata particularly when site conditions are affected by high levels of ambient road vibrations which are generally an obstacle to obtaining high quality MASW (Multichannel Analysis of Surface Waves) records (Kita et al, 2013). After the last report, we conducted several LAMS and MASW measurements at almost same time along the same survey lines using a common measurement system. As a result, we verified that dispersion curves obtained from LAMS measurements agreed well with the dispersion curves obtained via MASW measurements except that LAMS's dispersion curves also revealed phase velocities at lower frequency ranges. On the other hand, dispersion curves obtained via MASW measurements were more sensitive to changes of S-wave velocities in shallow layers than the dispersion curves obtained via LAMS. The authors have called this new survey approach which combines MASW and LAMS, the Hybrid Surface Wave Method. We verified that the Hybrid Surface Wave Method offers higher S wave structure resolutions and deeper investigation depths.