MULTI-CHANNEL ANALYSIS OF SURFACE WAVES
MASW
One of the most important factors in deciding the building codes is the ground stiffness.
In geotechnical engineering investigations, the traditional deflection-response method evaluates the stiffness by measuring stress-strain behavior of the materials caused by static or dynamic load. This method only measures the overall stiffness of a site. Furthermore, evaluation of a large-area geotechnical site by this method can be time-consuming and destructive to the pavements.
To evaluate each individual layers, the seismic tomography method utilizing boreholes can be used. However, it is also time-consuming, expensive, and intrusive.
Multichannel analysis of surface waves (MASW) provides a fast and convenient way to evaluate stiffness of underground soils and bedrocks.
Due to the inherent strong signals of surface waves (ground rolls), shear wave velocity profiling from MASW surveys are highly reliable even under various types of cultural noises, including the traffic problem which is a killer for traditional seismic reflection/refraction surveys in an urban environment.
While MASW cannot completely replace geotechnical borings in some cases, utilizing MASW in geotechnical investigations can still greatly reduce the number of borings necessary, save the time and the cost. It's greatly favorable especially in the urban environment where ground intrusion can be minimized.
MASW can also be used to locate underground voids. Compared to the resistivity method, it can be easily applied on the asphalt or concrete pavement without drilling holes for the electrodes. In addition, the affection from underground utilities is generally neglectable, making it more attractive over the resistivity method in urban environments.
Shear wave velocity profile
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A depth slice of 3D subsurface visualization of shear-wave velocity