A 24-channel seismograph deployed across a site off London Road captures the surface wave field that defines the ground stiffness profile. The geophones sit in a linear array, and a sledgehammer source generates Rayleigh waves that propagate through the glacial tills and river terrace gravels common across Ipswich. We process the dispersion curve in the field, extracting the fundamental mode to invert for shear wave velocity versus depth. The output is a VS30 value tied directly to the site classification required under Eurocode 8 for seismic design, even in this part of East Anglia where seismicity is low but the Building Regulations demand a defensible ground type. For deeper bedrock mapping we sometimes pair the MASW line with a seismic refraction profile to resolve the chalk interface that sits beneath the Quaternary cover in the Gipping valley.
A single MASW line gives you a continuous shear wave velocity profile from surface to 30 metres in under an hour of field time.
