The glacial till and alluvial deposits along the River Shannon create variable ground conditions across Athlone that standard boreholes alone cannot fully resolve. The town sits on a complex mix of gravels, sands, and clays deposited during the last glaciation, and the shear wave velocity profile can shift dramatically within a single site. We run multichannel analysis of surface waves (MASW) surveys to measure VS30 directly, giving engineers the data needed for Eurocode 8 ground type classification. A typical Athlone survey takes about two hours on site using a 24-channel seismograph with 4.5 Hz geophones, and we combine the results with in-situ permeability testing when groundwater conditions affect the seismic response. The deliverable includes a VS30 value, a shear wave velocity profile down to 30 metres, and the corresponding site class from A to E.
We deliver a VS30 value and Eurocode 8 ground type classification in under a week, based on actual shear wave velocity measurement, not correlation tables.
Service characteristics in Athlone
Risks and considerations in Athlone
We set out the 24-channel spread cable across the site with geophones planted at 2-metre intervals, using a sledgehammer on a steel striker plate to generate the surface wave train. The main challenge in Athlone is the shallow water table near the Shannon floodplain, which can dampen high-frequency signals and reduce resolution in the upper three metres. We counter this by adjusting the source offset and stacking multiple shots to improve the signal-to-noise ratio. Urban sites with buried services and hard standing also require careful array orientation, and we map out all known utilities before starting the survey. The inversion process is the critical step, and we run multiple iterations to ensure the modelled dispersion curve matches the field data with a root-mean-square error below five percent, eliminating non-unique solutions that could misclassify the site.
Our services
Our Athlone MASW service covers the full workflow from site mobilisation to the final interpretive report. Each survey is tailored to the site geometry and the ground conditions encountered.
VS30 Site Classification Survey
Full MASW survey with 24-channel acquisition, dispersion analysis, and VS30 calculation per Eurocode 8 travel-time method. Includes ground type A through E assignment for the structural designer.
Combined MASW and Refraction Tomography
Joint acquisition of surface wave and seismic refraction data using the same array, providing both shear wave velocity and P-wave stratigraphy for sites with complex bedrock topography.
2D Shear Wave Velocity Profiling
Multiple MASW arrays processed in parallel to generate a two-dimensional cross-section of shear wave velocity, suitable for sites with lateral variability such as river terrace deposits.
Site-Specific Response Spectra
Using the measured VS30 and shear wave velocity profile to generate site-specific elastic response spectra per Eurocode 8, replacing the default Type 1 or Type 2 spectra where local ground conditions warrant it.
Frequently asked questions
How much does a MASW survey cost in Athlone?
A single-array MASW survey to determine VS30 for a standard residential or commercial plot in Athlone ranges from €1,430 to €2,840. The price depends on site accessibility, number of arrays needed for 2D coverage, and whether we combine the survey with seismic refraction or other geophysical methods. We provide a fixed-price quote after reviewing the site location and project requirements.
What is VS30 and why does it matter for my Athlone building project?
VS30 is the time-averaged shear wave velocity in the top 30 metres of the ground. Eurocode 8 uses VS30 to classify the site into ground types A through E, which determines the seismic design spectrum and the forces your structure must resist. In Athlone, where glacial deposits create variable stiffness with depth, a measured VS30 prevents both under-design and unnecessary over-engineering of foundations.
How long does a MASW test take and when do I get results?
Fieldwork for a single MASW array in Athlone typically takes two hours, including setup, calibration shots, and main acquisition. Multiple arrays for 2D profiling extend this proportionally. The data processing and inversion are completed back at the lab, and we issue the final report with VS30, ground type classification, and shear wave velocity profile within four to six working days of the survey.