Assessment of an MASW technique incorporating discrete particle modelling

A Discrete Particle Scheme (DPS) consisting of interacting circular particles is
utilised to examine the Multichannel Analysis of Surface Waves (MASW) technique.
Synthetic earth models of various complexity are generated using the DPS and analysed
by the MASW dispersion and inversion techniques. For normally dispersive cases,
dominated by the fundamental mode, the MASW profiles closely match the true synthetic
shear wave velocity (Vs) profiles. When tested on a model that contains a low velocity
layer, the accuracy is reduced.
MASW field tests at a highly uniform site in Norway (Onsøy) and a site with
distinctive layer boundaries in Ireland (Ballinasloe) result in highly repeatable profiles of
Vs. Resolution of dispersion curves at low frequencies (<10Hz) is a problem at the
Ballinasloe test site, which limits the depth of penetration of the technique. MASW
inversion results compare excellently with downhole seismic cone tests at the Onsøy test
site and reasonably with a seismic refraction survey at the Ballinasloe site.