Frequently asked questions.

In short: ReMi® gives you more usable data, in less time, with greater reliability — even in conditions where MASW may fail. MASW works under ideal conditions. Terēan-compliant ReMi® works under real conditions.

• ReMi® is easier, faster, collects more usable data, and produces more reliable results across a wider range of sites.
• Terēan ReMi® surveys take less time to collect (typically just 10–15 minutes of recording) and allow for real-time field QC with a single button click.
• Even though MASW takes longer in the field, it captures only about one tenth the amount of wave data as a Terēan ReMi® survey.
• With more input data, Terēan ReMi® produces higher-quality and more stable results across a wider range of geologies — including noisy, complex, and non-dispersive conditions.
• MASW assumes the active source generates the strongest waves at the site, at all frequencies. In busy or urban environments, this is very difficult to achieve. Terēan ReMi® does not rely on this assumption, which is why it delivers compliant results at quiet, noisy, paved, sloped, and space-limited sites.

ReMi® and MASW both use surface waves, but they work very differently — and those differences matter on real job sites.

In short: MASW requires perfect field conditions and struggles with low-velocity zones and noisy sites. ReMi® is easier to collect, more forgiving, better at resolving complex layering, and easier to tie to boreholes.

MASW

• Requires precise, hands-on field collection with controlled active shots and perfect timing.
• You can’t just let it run — the source and receiver geometry must be tightly controlled.
• Struggles on noisy or busy sites, where dispersion curves from the active shots get buried beneath noise.
• Has difficulty identifying low-velocity zones, especially when they are thin or beneath stiff layers.
• Often breaks down in non-dispersive or stiff soils, where dispersion curves flatten out.
• Ties to boreholes less effectively because it typically relies on picking a single dispersion curve, which may not match deeper layers.

ReMi®

• Analyzes the full wavefield in the slowness–frequency (p–f) domain rather than relying only on spectral peaks.
• Much more tolerant of weak or flat dispersion, making it more reliable in stiff, uniform, or non-dispersive geology.
• Performs extremely well in noisy, real-world environments. Ambient noise actually helps the method.
• Can run with both passive and active energy, so you can let it record while doing other tasks.
• Easily identifies low-velocity zones because the full p–f image captures layering that MASW may miss.
• Easy to tie to boreholes, since the deeper velocity structure is represented more completely.
• Ideal for Vs30/Vs100, depth-to-bedrock, rippability, fault imaging, mapping liquefaction potential, imaging landslides, and other general geotechnical work.

Even in non-dispersive settings, the ground still generates Rayleigh waves. Because ReMi® analyzes slowness–frequency (p–f) energy instead of relying solely on traditional dispersion picking, it is more tolerant than traditional MASW and can still produce stable results even when shear-wave velocities change only slightly with frequency.

In areas with shallow, high-velocity bedrock, we may recommend tighter geophone spacing to help resolve thinner, softer layers above rock. Because every site is different, you can review your data in real time or send it to our team with one click for immediate expert feedback.

All Terēan systems provide more than 100 ft of depth resolution. Depth capability increases with channel count and array length:

• 24-channel system: 1D profiles typically image 300+ ft; 2D sections typically image 150+ ft.
• 120-channel system: can image 3,000+ ft.

Yes. Our systems work great at both quiet and noisy job sites. In fact, noise can actually help the data by adding extra energy into the ground. You just check the record quality in real time using our simple one-click QC tool to make sure everything looks good.

Most 24-channel lines can be set up, recorded, and wrapped up in about 30 minutes.

And the best part — the same 1D site-class data you collect is the exact data we use to generate your full 2D section. No extra steps needed.

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

Typical applications include:

• Seismic site classification (Vs30 / Vs100)
• Depth-to-bedrock determination
• Fault imaging
• Void detection (i.e., karstic environments and lava tubes)
• Rippability assessments
• Landslide plane mapping
• Optimizing borehole programs
• Geotechnical, mining, water resources, energy, and infrastructure investigations

No. Terēan systems are designed for engineers, drillers, and field technicians with little or no geophysical background. When you purchase a system, Terēan geophysicists become part of your team, available whenever you need support.

We train you on a real project of your choice and deliver a billable report, so you can begin recovering your investment on day one.

With complimentary training, ongoing support, and discounted processing, you can collect and deliver fully compliant data with confidence from the very start.

In addition to your complimentary in-person training, you receive unlimited access to our geophysicists for field planning and collection guidance, QC review, processing support, and project-specific recommendations. This support continues for the duration of your included service period, with the option to renew to keep full access to our team.

Once data is submitted, our value-priced standard turnaround is 2 weeks. Rush delivery options are available with 24–48 hour turnaround.

ReMi® is designed to be collected almost anywhere — even in tight or challenging spaces. If your site is space-limited, just give us a call. A Terēan geophysicist will help you plan your survey and review your data live during collection to confirm you’re reaching your depth goals. We do this often, so we’ve made it simple: send us your records during data collection with a single click.

• Quiet site? Add a few extra hammer hits.
• Noisy site? Perfect! Ambient noise helps — just make sure your dispersion image looks clear during acquisition, with a single button click.
• Steep slopes? Our software corrects for topography during processing.
• Concrete or hard surfaces? Use our hard-surface bases.

If you can lay out a line of geophones, we can make it work.

ReMi® records both passive and active energy continuously, so you can collect Vs30/Vs100 data while borings are being logged. The drill rig vibrations simply add to the natural background noise and often improve the data. This lets you multitask on site — reducing mobilizations, saving time, and lowering project costs.

This is a misconception. HVSR does not predict Vs. HVSR peak frequencies only give the ratio of velocity to interface depth.

HVSR can collect corroborating depth-to-bedrock estimates, but only when tied to Vs from ReMi®. HVSR–ReMi® comparisons, with correlations to wells, are available in the Sturmer & Louie USGS report ↗.

Terēan-compliant ReMi® surveys do not require circular arrays.

We always use an in-line active source (hammer strikes with a 10+ lb sledgehammer), which provides the controlled Rayleigh-wave energy needed for accurate, ASCE/IBC compliant, and defensible results.

Circular arrays are only required in purely passive microtremor array methods. Because Terēan ReMi® always incorporates active hits, a straight-line array is the appropriate and industry-standard configuration.

There is no recent literature suggesting this. The misconception comes from a single paper published more than a decade ago in which the authors collected non-compliant ReMi data (no active source, very few records) and then requested non-compliant processing. Unsurprisingly, the results were poor, but this does not represent compliant ReMi® acquisition, modern workflows, or how the method was originally designed and validated.

This paper has unfortunately circulated without context, leading to confusion about the reliability of ReMi®. Terēan-compliant ReMi® avoids these issues entirely.

Your purchase includes complimentary training, standardized acquisition protocols, and ongoing support from geophysicists with over 20 years of ReMi® acquisition & processing experience. We ensure that your data is collected correctly and that your results are accurate, defensible, and compliant.

We care deeply about data quality because your structures, and the people who rely on them, depend on accurate subsurface characterization.

Most projects require only one linear array with ~20 records (takes just 10 minutes), combining passive and active energy. This approach produces stable, repeatable Vs profiles.

Some firms collect two arrays in an X-formation for redundancy. This adds ~30 minutes of field time. The resulting Vs100 is typically within ±5 ft/s.

Owning a Terēan system gives you the flexibility to create your own standards, supported by our team to ensure full compliance and high-quality results.