ACTIVE SURFACE-WAVE PROFILING
Multichannel Analysis of Surface Waves (MASW)
Characterise near-surface shear-wave velocity through multichannel recordings, dispersion-curve interpretation and transparent inversion assumptions.
ENGINEERING OVERVIEW
From surface waves to shear-wave velocity
Multichannel Analysis of Surface Waves (MASW) is a seismic method that uses recordings from an array of geophones to analyse the dispersion of surface waves and estimate a shear-wave velocity (Vs) profile. Active MASW typically uses a controlled source; passive variants may be used where site conditions support them. The Vs profile comes from inversion, so wave-mode identification and geological constraints are essential.
Ground stiffness varies between boreholes, and a single test may not represent an entire alignment. MASW can provide a low-disturbance velocity constraint across a corridor or engineering site, supporting stratigraphic interpretation and seismic site assessment. Its value is highest when the designer understands which wavelength ranges were actually recorded and which parts of the model are well constrained.
MEASUREMENT & INTERPRETATION
What the method actually tells you
Recorded wavefield
A controlled impact or mechanical source generates surface-wave energy recorded across multiple receiver channels.
Dispersion is the observable
Measured phase velocity changes with frequency and wavelength. This relationship is used to infer the distribution of shear-wave velocity with depth.
Modes require care
Fundamental and higher surface-wave modes may overlap or dominate in different ground conditions; picking the wrong branch can distort the inverted Vs profile.
Pseudosection is not a borehole log
Adjacent 1D inversions may be presented as a 2D-style section, but lateral resolution and assumptions must be acknowledged.
PRACTICAL SURVEY FLOW
From site question to defensible interpretation
Define the target depth
Identify required Vs interval, level of engineering uncertainty and access restrictions.
Set spread and source
Select receiver spacing, line length, energy source, shot offsets and acquisition windows for expected wavelengths.
Review dispersion
Inspect field traces, signal-to-noise ratio, coherent energy and possible mode mixing before inversion.
Invert and integrate
Estimate Vs models, test sensitivity and compare with MAM, refraction, drilling or relevant dynamic tests.
WHERE IT ADDS VALUE
Engineering applications and use cases
Seismic site characterisation
Constrain shear-wave velocity for dynamic ground-response understanding and project-specific parameter selection.
Infrastructure corridors
Screen lateral variation in near-surface stiffness along roads, transport alignments or construction footprints.
Investigation optimisation
Help determine where supplementary boreholes or targeted testing could most reduce ground-model uncertainty.
MEASUREMENT BOUNDARIES
Limitations and conditions of use
Interpretation quality depends as much on survey suitability and independent evidence as on processing software.
- Limited spread length and low-frequency energy may constrain deeper investigation.
- High-frequency attenuation, pavement coupling and site access can limit shallow resolution.
- Higher-mode interference, lateral changes and inversion non-uniqueness can produce plausible but different Vs profiles.
- Vs does not uniquely define lithology, undrained shear strength or bearing resistance.
METHOD SELECTION
How to choose the right approach
MASW versus MAM
Active MASW controls the source timing and geometry; passive MAM relies on the ambient wavefield and its spatial statistics.
MASW versus seismic refraction
MASW focuses on dispersion and Vs; refraction analyses first arrivals and can better constrain certain compressional-velocity interfaces.
MASW versus borehole crosshole
MASW samples surface propagation over a line; crosshole testing uses controlled subsurface source–receiver paths at specific depths.
Select MASW where near-surface Vs is central to the engineering question and suitable line access exists. Pair with MAM where passive long-wavelength constraints would improve the investigation, and avoid promising fixed penetration or resolution without field design.
ENGINEERING ASSURANCE
Field quality, interpretation and review
A traceable project record should retain the following information where applicable:
- Source and geophone geometry, sampling and coupling logs
- Repeated shots and raw record quality, including traffic/cultural noise
- Dispersion-image evidence and justification for selected wave modes
- Inversion misfit, reasonable alternate models and borehole consistency checks
PROJECT DELIVERABLES
What a useful technical report should contain
01 · Project output
Geophone and shot layouts with acquisition parameters
02 · Project output
Raw waveforms and selected dispersion information
03 · Project output
Vs profiles or interpreted sections with inversion assumptions
04 · Project output
Engineering interpretation, confidence bounds and recommended ground truth
COMMON QUESTIONS
Frequently asked questions
Is MASW a direct measurement of shear-wave velocity at depth?
Can MASW distinguish soil and rock precisely?
How is MASW different from MAM?
TECHNICAL REFERENCES
Further technical reading
- USGS — Multichannel analysis of surface waves
- USGS — MASW receiver-spread assumptions
- USGS — Multimethod seismic site characterisation
References describe the underlying methods and recommended data-quality principles; interpretation for any particular site must address its own evidence and constraints.
PROJECT ENQUIRIES
Discuss your ground investigation challenge.
GEOOE · GEOORIGIN ENGINEERING LIMITED
Share the site location, investigation objective, expected depth range, available boreholes and decisions the results need to support. We can discuss appropriate technical methods, limitations and project-specific collaboration.