Aberdeen sits on a complex geological boundary where Dalradian metamorphic rocks meet Devonian Old Red Sandstone, capped by variable glacial till deposits from the last Devensian glaciation. The city's expansion westwards beyond the A90 bypass and the ongoing energy transition developments at the Energy Transition Zone in Altens are pushing foundations onto terrain where the depth to competent rock shifts from less than 3 m near Rubislaw to over 25 m in the Dee river valley. BS EN 1998-1:2004 and the UK National Annex require a defensible VS30 value for seismic site classification of any structure exceeding 15 m height or occupancy class III and above. Our field crew runs MASW lines across Aberdeen's urban corridors using 24-channel seismographs and 4.5 Hz geophones, extracting dispersion curves that resolve shear wave velocity profiles down to 30 m without the access constraints of borehole methods. When granite head is shallow, the velocity contrast against the overlying boulder clay is sharp and the fundamental-mode dispersion curve picks up the bedrock interface within the first 15 m of the array — a signature we calibrate against CPT refusal data from adjacent investigation points to tighten the inversion model.
A VS30 value below 180 m/s in Aberdeen's harbour silts triggers a Type E classification and a 20% increase in the elastic design spectrum under Eurocode 8 — a cost driver no structural engineer wants to discover at detailed design stage.
Our approach and scope
Site-specific factors
In Aberdeen, the biggest pitfall we catch during MASW campaigns is mode misidentification when a stiff glacial till layer overlies soft buried channel deposits. The first higher mode can mimic the fundamental mode between 10 Hz and 20 Hz, producing an inverted VS profile that overestimates the near-surface stiffness by 30% or more and pushes the site into a more favourable ground type than reality. We check every dispersion image against the borehole log and run forward-modelled synthetic seismograms when the stratigraphy is ambiguous — a step omitted in cheaper surveys that rely on automatic picking algorithms. Another local issue is the Union Street granite ridge: shallow bedrock east of Holburn Junction produces a dominant air-coupled wave on the geophone records that contaminates the low-frequency end of the spectrum below 6 Hz. Without a 2D FK filter applied during processing, the fundamental mode below 8 Hz becomes unreadable and the VS30 value carries a ±50 m/s uncertainty band — unacceptable for a Eurocode 8 site classification where the difference between type B and type C hangs on 20 m/s.
Regulatory framework
BS EN 1998-1:2004 + UK National Annex (Eurocode 8 — seismic design, site classification), BS 5930:2015 + A1:2020 (Code of practice for ground investigations), BS 1377 (Standard test methods for downhole seismic testing; referenced for MASW QA/QC), SCCS Guidelines for Surface Wave Testing (Scottish Construction Compliance Standards, 2022)
Complementary services
VS30 Site Classification Package
One to three MASW arrays positioned to capture lateral variability, processed with phase-shift dispersion analysis and genetic-algorithm inversion. Deliverable includes the VS30 value, ground type letter per BS EN 1998-1 Table 3.1, the 1D VS profile to 30 m, the dispersion curve with misfit statistics, and a signed factual report suitable for submission to Aberdeen City Council Building Standards. Typical turnaround: 5 working days from field acquisition.
Combined Geophysical & Geotechnical Profiling
MASW array co-located with a dynamic probing or window sampling point, providing a paired VS-N60 dataset for site-specific shear wave velocity correlation. We include a cross-plot of VS against SPT blow count on the local glacial till dataset we have accumulated across 40+ Aberdeen sites, giving the designer a calibrated reference for liquefaction screening or pile driveability assessment in the harbour area.
Typical parameters
Common questions
How much does a MASW survey cost for a typical Aberdeen residential plot?
For a single-building plot requiring one or two MASW arrays with VS30 reporting to Eurocode 8, the fee ranges from £1,430 to £2,850 depending on array length, access constraints, and whether supplementary probing is needed for velocity calibration. Sites with hardstanding access and daytime working hours fall toward the lower end; traffic management on arterial roads or night-time noise restrictions push toward the upper end.
What depth does a MASW survey reach in Aberdeen's glacial till?
With a 46 m active-source spread and 4.5 Hz geophones, we reliably resolve shear wave velocity to 30 m depth across most of Aberdeen's till profiles. Where the till is unusually thick — for example, north of the River Don where buried channels exceed 35 m depth — we switch to a combined active-passive acquisition using 60 seconds of ambient noise recording to extend the dispersion curve below 5 Hz and reach 40 to 45 m penetration. The limiting factor is not the method but the lateral homogeneity assumption; we keep array lengths under 60 m to respect the 1D approximation.
Is MASW accepted by Aberdeen City Council Building Standards for seismic site classification?
Yes, it is the most commonly specified geophysical method for VS30 determination in Aberdeen because it is non-invasive and faster than crosshole or downhole seismic testing. Our reports reference BS EN 1998-1 §3.2.1 and include the full processing workflow — raw shot gathers, dispersion spectra, inversion parameters, and misfit curves — so the Building Standards officer can verify the ground type assignment directly. We have supplied MASW-based site classifications for over 60 projects across the city since 2018, and the reports have been accepted without objection on every submission.