MASW for ‘stiffness’ of the ground

Geotechnical engineers require accurate parameters for designing buildings, foundations, rock slopes and so forth. The shear-wave velocity of the ground is a useful part for determining common geotechnical parameters such as Poisson’s Ratio and Shear Modulus.

Shear-waves are notoriously difficult to measure directly because they are slower than P-waves and thus are imbedded in the complex wavetrain.  Typically, they are recorded directly using boreholes.  However, where boreholes are not available, standard low-frequency vertical geophones are used with shots taken off both ends of the spread.  ClearView typically acquires these off-end shots as part of standard refraction surveys in order to calculate shear-wave velocities with depth.

Vs30 is also calculated as part of the MASW process.

ClearView can also use passive surface wave methods to generate dispersion curves using SPAC (Spatial Autocorrelation).  Passive waves are generally lower frequency from randomly distributed and triggered sources. Examples of cultural sources include vehicles and machinery.  Natural sources include wind and water waves.  ClearView uses ParkSEIS software for MASW and Interpex software for refraction analyses and interpretation.