Listening to the ground.

Refraction Microtremor (ReMi®) uses the vibrations already moving through your site — traffic, machinery, wind — plus a few hammer hits, to image the shear-wave velocity of the ground below. No drilling required to see the whole line.

Schedule a Demo ReMi® vs. MASW

The idea

Stiff ground is fast. Soft ground is slow.

Shear-wave velocity (Vs) is how fast shear waves travel through soil and rock — a direct measure of stiffness. Loose, saturated soils are slow; dense soils are faster; bedrock is fastest. Building codes use the average Vs of the upper 100 ft (Vs100, or Vs30 in meters) to classify how strongly a site will shake in an earthquake.

Surface waves of different frequencies “feel” different depths — longer wavelengths reach deeper. By recording how those waves travel along a straight line of geophones, ReMi® works out how velocity changes with depth, and lateral changes along the line.

Ambient noise is the energy source. In fact, a noisy site helps: traffic, drill rigs and machinery simply add energy into the ground.

A straight line of geophones records passive noise and in-line hammer hits together — the standard Terēan®-compliant ReMi® setup.

In the field

From setup to site class — often before lunch.

01 ~30 min
Deploy

Lay out a straight line of geophones — typically 24 channels — on soil, pavement, slopes or tight sites. Hard-surface bases handle concrete and asphalt.
02 10–15 min
Record

Collect ~20 records combining passive ambient noise with active hammer hits from a 10+ lb sledge. Keep recording while borings are logged — drill-rig vibration helps.
03 1 click
QC in the field

Check record quality live with the one-click QC tool, or send records to a Terēan geophysicist for immediate feedback — before you leave the site.
04 p–f domain
Analyze

VsSurf analyzes the full wavefield in the slowness–frequency (p–f) domain rather than just spectral peaks — more tolerant of noisy, stiff or non-dispersive sites.
05 < 30 min
Report

Auto-generate a 1D Vs profile and ASCE 7-22 site class report. The same data builds a full 2D section — no extra field steps.

ReMi® vs. MASW

MASW works under ideal conditions. Terēan-compliant ReMi® works under real ones.

Both use surface waves, but they work very differently — and on real job sites, those differences matter.

MASW Terēan ReMi®

Field collection

MASWPrecise, hands-on collection with controlled active shots and perfect timing — source and receiver geometry must be tightly controlled.

ReMi®Records passive and active energy together, so you can let it run while doing other tasks. Typically 10–15 minutes of recording.

Noisy / busy sites

MASWStruggles — dispersion from the active shots gets buried beneath noise.

ReMi®Performs extremely well. Ambient noise actually helps the method.

Low-velocity zones

MASWDifficulty identifying LVZs, especially thin ones beneath stiff layers.

ReMi®Easily identifies LVZs — the full p–f image captures layering MASW may miss.

Stiff / non-dispersive soils

MASWOften breaks down where dispersion curves flatten out.

ReMi®Much more tolerant of weak or flat dispersion; still produces stable results.

Amount of wave data

MASWAbout one tenth the wave data of a Terēan ReMi® survey.

ReMi®More input data → higher-quality, more stable results across more geologies.

Tie to boreholes

MASWLess effective — usually relies on picking a single dispersion curve.

ReMi®Easy — the deeper velocity structure is represented more completely.

Ideal for Vs30/Vs100, depth-to-bedrock, rippability, fault imaging, mapping liquefaction potential, imaging landslides, and general geotechnical work. More in the FAQs →

How deep?

Every Terēan system resolves more than 100 ft.

Depth capability grows with channel count and array length. A standard 24-channel line typically images 300+ ft in 1D and 150+ ft in 2D; larger arrays reach thousands of feet for mineral, water and energy work.

Bars are on a logarithmic scale.

24-channel · 2D sections150+ ft

24-channel · 1D profiles300+ ft

Deep ReMi®1,000+ ft (300 m)

120-channel system3,000+ ft

Basin-scale energy imaging10,000+ ft (3,200 m)

Any array, any scale

VsSurf works with geophone arrays, DAS fiber, small and large recording setups, and both interferometric and non-interferometric data.

Triggerless P-wave acquisition

Terēan invented triggerless P-wave acquisition — eliminating cables, trigger errors and timing issues, making P-wave surveys faster and simpler than ever.