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Seismic Tomography for Site Investigation in Dublin

Site investigations you can build on.

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Dublin's expansion beyond the canals into areas like Cherrywood and Adamstown has pushed development onto terrain shaped by the last glaciation. Limestone bedrock, buried channels of the Liffey, and pockets of glacial till create a subsurface that can change radically within a single site. A standard borehole grid often misses the lateral transitions between competent rock and soft, compressible deposits. Seismic tomography fills that gap by mapping P-wave and S-wave velocity across a continuous profile, revealing exactly where the rockhead drops or where dissolution features weaken the load-bearing strata. For foundation design on Dublin's complex geology, this is not a supplementary survey—it is the fastest way to build a defensible ground model before committing to deep excavations or piling. When combined with targeted test pits, the velocity model can be calibrated against actual soil descriptions, turning geophysical assumptions into engineering-grade data.

Seismic tomography turns a sparse set of borehole logs into a continuous cross-section, reducing the guesswork in Dublin's highly variable glacial terrain.

Process overview

A recent project near the Grand Canal Dock involved a six-storey office block where the initial boreholes hit limestone at 4 m on one side but found soft alluvium to 10 m on the other. We ran a 94 m refraction line with 4.5 Hz geophones at 2 m spacing, using a 10 kg sledgehammer source. The tomographic inversion showed a buried channel trending northeast, filled with low-velocity material—classic Liffey paleochannel behaviour. That single survey changed the piling design from uniform 8 m sockets to a zoned layout with deeper elements along the channel axis, saving the developer roughly three weeks of overburden drilling in hard ground. The method works well in urban noise if you stack shots and run surveys during quieter hours. For deeper targets beyond 30 m, we often pair this with seismic refraction to extend the depth of investigation without losing the lateral resolution that tomography provides across the near-surface.
Seismic Tomography for Site Investigation in Dublin
Technical reference — Dublin

Local context

The Carboniferous limestone that underlies most of Dublin is susceptible to karstification, particularly along the Castleknock and Clondalkin belts. Where acidic groundwater has enlarged joints and bedding planes, you get voids and soft infill zones that cannot be reliably detected by probing alone. A velocity anomaly below 1,200 m/s in what should be competent rock is a red flag that demands follow-up. Even without karst, the transition from lodgement till to weathered rock can mimic bedrock in standard penetration tests, leading to false refusal and dangerously short pile sockets. The cost of missing a dissolution feature runs well beyond redesign—piling rigs have been lost into collapsed cavities in the greater Dublin area. Seismic tomography reduces this risk by giving the geotechnical engineer a continuous image of the rock surface and any low-velocity zones within it, before a single pile is cast.

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Reference standards


ASTM D5777-18: Standard Guide for Using the Seismic Refraction Method, Eurocode 7 (EN 1997-1:2004) – Geotechnical Design, Section 3.3 on Ground Model, ISRM Suggested Methods for Seismic Testing, BS 5930:2015+A1:2020 – Code of Practice for Ground Investigations

Technical data

ParameterTypical value
Source typeAccelerated weight drop or sledgehammer
Geophone spacing1 m to 5 m depending on target resolution
Recording system24-channel seismograph, 24-bit A/D
P-wave penetration (refraction)Typically 15 m to 50 m with impact source
S-wave capabilityHorizontal source for Vs profiles
Inversion algorithmRay tracing with iterative least-squares
Output deliverables2D velocity sections, depth-to-bedrock maps, Vp/Vs ratios

Common questions


How much does a seismic tomography survey cost in Dublin?

For a typical Dublin site requiring a single 100-metre refraction line with tomography processing, budgets run between €2,270 and €4,680. The range depends on line length, source type (sledgehammer vs. weight drop), traffic management requirements, and whether we process P-wave only or add S-wave data for a full Vs profile.

What depth can seismic tomography reach in Dublin's geology?

With a 115-metre spread and a weight drop source, we routinely image to 45–55 metres in limestone. In glacial till overburden, penetration drops to around 20–30 metres because the till absorbs high-frequency energy. For deeper targets, we extend the spread length or use a more powerful source after assessing site access.

Can you run seismic surveys on busy streets in Dublin city centre?

Yes, with careful planning. We use triggered recording and high-stack counts to overcome traffic noise. Surveys are often scheduled for early morning or Sunday hours to reduce interference. Geophones are planted on asphalt using base plates, and the line is cleared within the same shift—no overnight road occupation needed.

How do you calibrate the velocity model with real soil data?

The reference range for this service in Dublin is €2.270 - €4.680. The final price depends on the project scope and volume.

Location and service area

We serve projects across Dublin and surrounding areas.

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