Glasgow's geology is deceptive. Beneath the Victorian sandstone tenements and modern regeneration projects, you'll find a complex mixture of glacial till, sand and gravel, and the notorious coal measures that undercut much of the city centre. The British Geological Survey maps show over 150 abandoned mine entries within the city boundary alone. When a developer on the Clyde waterfront needed VS30 values for a 14-storey residential tower, the upper 30 metres revealed shear wave velocities varying from 180 m/s in the alluvial clays to over 350 m/s in the dense till beneath. That kind of contrast matters for seismic site classification under Eurocode 8. Our team runs the MASW survey with 24-channel geophone arrays, processing the fundamental-mode dispersion curve to extract a 1D shear wave velocity profile that feeds directly into the ground model. For deeper bedrock mapping beyond 30 metres, we often combine with a seismic refraction line to resolve the till-rock interface that's critical for piled foundation design.
Vs30 is not just a number for the Eurocode checklist. It dictates the spectral shape of the design earthquake and can shift your site by a full ground type.
Process and scope
In Glasgow, we've learned that the single most important factor in a successful MASW campaign is source coupling. The urban environment here is noisy—buses on Dumbarton Road, piling rigs on adjacent sites, even the Underground trains running below St Enoch Centre generate vibrations that contaminate records. We use a 10 kg sledgehammer on an aluminium plate with three to five vertical stacks per shot point, and we'll often run surveys on a Sunday morning when background noise drops. The raw shot gathers go through a dispersion-imaging algorithm we've calibrated against downhole data from multiple Glasgow sites. What we're really after is the Rayleigh wave phase-velocity dispersion: picking the fundamental mode from 5 Hz up to 30 Hz, then inverting to obtain Vs versus depth. The process follows BS EN 1997-2 Section 4.2 for indirect ground investigation, and every profile includes a misfit analysis so you can see the inversion quality.
Key specifications we work to: a minimum array length of 46 metres for 2-metre geophone spacing, record lengths of 2 seconds, and sampling at 0.5 ms intervals. For sites in Pollokshields or Shawlands where the drift thickness can exceed 40 metres, we extend the array to 69 metres with 3-metre spacing to push the investigation depth past 35 metres. The deliverables include Vs30 calculated to BS EN 1998-1, the travel-time-averaged shear wave velocity for the upper 30 metres, which determines whether your site falls into ground type B, C, D, or E. We also provide the full 1D velocity model, the dispersion image, and a site classification letter suitable for building warrant submission.
Site-specific factors
A hotel project on Argyle Street went to tender with a desktop study assuming ground type B based on regional mapping. The client decided to verify with MASW before finalising the foundation design. The survey returned a Vs30 of 195 m/s across most of the site—ground type C, one category softer than assumed. Under Eurocode 8, that single reclassification increased the design spectral acceleration by roughly 20% in the short-period range, which meant re-analysing the lateral-load system for the piled foundation. Had they skipped the measurement and built to the optimistic assumption, the structure would have been under-designed for the seismic demand. Glasgow is in a low-to-moderate seismicity region, but the UK National Annex to Eurocode 8 still requires site classification for structures over 5 storeys. We've seen similar reclassifications on former industrial sites along the Clyde where shallow made ground and soft alluvium mask the faster material below. The cost of a MASW survey is negligible compared to the liability of a wrong ground-type assumption in the SER certification.
Questions and answers
What does a MASW survey cost for a typical Glasgow site?
For a single-array MASW survey on a standard Glasgow residential or commercial site, the cost ranges from £1,330 to £2,180 depending on array length, access conditions, and whether additional arrays are needed to cover a larger footprint. A site with restricted access or extensive made ground may require more setup time. We provide a fixed-price quote after reviewing the site location, geology, and the number of measurement points required.
How deep can MASW investigate in Glasgow's glacial till?
With a 2-metre geophone spacing and a 46-metre array, we typically resolve Vs to 25–30 metres depth. Where the till thickness exceeds 30 metres—common in parts of Pollok and the southern suburbs—we switch to 3-metre spacing and a 69-metre array, pushing the investigation depth past 35 metres. The limiting factor is the longest recovered wavelength, which depends on array length and the stiffness contrast between layers.
Is MASW accepted by Glasgow City Council building control?
Yes. MASW-derived Vs30 and site classification are accepted by Glasgow City Council and by SER certifiers when the survey is carried out to BS EN 1997-2 and the results are interpreted by a competent geophysicist or geotechnical engineer. We include a site classification letter with every report, referencing the relevant clauses of BS EN 1998-1 and the UK National Annex, which satisfies the requirements for building warrant submission.
Can you run MASW on a site with existing foundations or buried services?
We can, but it requires careful array layout to avoid coupling issues. Buried services like gas mains or high-voltage cables generate no significant interference as long as the geophone array is offset by at least 2 metres. Existing slab foundations are more problematic—the concrete creates a high-velocity surface layer that can mask the fundamental Rayleigh mode. In those cases, we deploy the array on adjacent soft ground or, if that's not possible, we use a downhole method in a borehole instead.
How long does a MASW survey take and when do we get the report?
Fieldwork for a single-array MASW survey takes about two to three hours on site, including setup, testing, and demobilisation. If we're running multiple arrays across a larger site or combining with seismic refraction, it can take a full day. The report with the Vs30 value, 1D velocity profile, dispersion image, and site classification letter is delivered within five working days of the survey. We can expedite to 48 hours if the SER submission deadline is tight.
