When it comes to subsurface investigations, two prominent seismic methods are often employed: Multichannel Analysis of Surface Waves (MASW) and downhole seismic testing. Both techniques aim to determine the shear wave velocity (Vs) profile of the ground, which is crucial for various geotechnical and seismic applications. However, they differ significantly in their methodologies, data acquisition processes, and the nature of the results they produce.
Multichannel Analysis of Surface Waves (MASW)
MASW is a non-invasive seismic method that analyzes surface waves to evaluate the subsurface shear wave velocity profile. It involves generating seismic waves at the surface, typically using an active source like a sledgehammer, and recording the resulting wavefield with an array of geophones arranged linearly on the ground surface. The key steps in MASW include:
- Data Acquisition:An active seismic source generates surface waves, which are captured by multiple geophones placed at regular intervals along a line.
- Dispersion Analysis:The recorded data are processed to extract dispersion curves, which depict the variation of surface wave velocity with frequency.
- Inversion:The dispersion curves are inverted to obtain a shear wave velocity profile with depth.
MASW is particularly advantageous for its efficiency and ability to provide a continuous 2D profile of shear wave velocities. It is well-suited for mapping lateral variations in subsurface materials and is commonly used in geotechnical engineering, environmental studies, and earthquake site response analyses.
