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Seismic Tomography (Refraction & Reflection) for Site Characterization in Irving, Texas

Site investigations you can build on.

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More than once we've seen a project team in Irving assume the Eagle Ford Shale is uniform and shallow, only to hit a deep paleochannel or an undocumented fault scarp during excavation. That assumption can add weeks to a schedule and tens of thousands in change orders. The Dallas County subsurface, particularly where the Woodbine Formation transitions toward the Balcones Fault Zone, is anything but predictable. Seismic tomography (refraction/reflection) cuts through that guesswork by building a continuous 2D or 3D velocity model from the surface, letting us map bedrock topography, identify low-velocity zones, and flag karst-like features in the Austin Chalk before a single bucket bites the dirt. For sites where conventional borings miss lateral heterogeneity, combining our seismic surveys with targeted sondaje SPT gives you both the geophysical signature and the physical sample to calibrate it—because interpreting a velocity anomaly without a ground-truth boring is just educated guessing.

A single Irving borehole tells you what's at one point; a seismic tomography line tells you what's happening across 200 feet—and what you're about to excavate into.

Our service areas

Process and scope

Irving sits at roughly 482 feet above sea level, straddling the Trinity River floodplain and the rolling uplands that climb toward DFW Airport. The city's explosive growth—pushing past 256,000 residents according to the 2020 Census—has put pressure on marginal land that older developments bypassed. What we find repeatedly is that seismic velocity contrasts in the upper 100 feet can swing by a factor of three across a single parcel, especially near the Camp Wisdom or West Irving Creek drainages where alluvial sands and gravels overlie weathered shale. A well-designed seismic tomography survey uses a 24- or 48-channel geophone spread and a weight-drop or accelerated hammer source to generate P-wave and S-wave arrivals; we then invert travel times with ray-tracing algorithms to resolve layers as thin as 3 to 5 feet. When reflection targets are needed for deeper structure—say, confirming the top of the Ellenburger limestone at 300+ feet for a deep foundation—we deploy a higher-energy source and tighter CDP spacing. The resulting velocity sections feed directly into IBC site class determination (A through F) and can be integrated with downhole seismic CPT to refine the small-strain shear modulus profile for liquefaction triggering analysis.
Seismic Tomography (Refraction & Reflection) for Site Characterization in Irving, Texas
Technical reference — Irving

Site-specific factors

North Texas doesn't get the seismic attention that California does, but Irving sits within the Fort Worth Basin, and the USGS now maps induced seismicity hazard across the metroplex at levels that influence design—particularly for essential facilities. The bigger risk for most projects, however, is differential settlement driven by buried channel deposits that a standard grid of borings can miss entirely. We've mapped paleochannels 30 feet deep cutting through otherwise competent shale; a footing bridging that contact behaves like a hinge. The seasonal shrink-swell cycle of the upper clay adds another wrinkle, because the same low-velocity near-surface layer that seismic refraction interprets as weathered rock in August can look like saturated soft clay in March. That's why we run surveys with multiple shot points and reciprocal travel-time checks—if the plus-minus time-distance analysis doesn't close within 5%, we re-shoot the line. In areas east of Loop 12 where the floodplain deposits thicken, the combination of seismic tomography and laboratory grain-size analysis on auger samples gives us the cross-check needed to separate truly low-modulus material from velocity degradation caused by partial saturation.

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Reference standards

ASTM D5777 – Standard Guide for Using the Seismic Refraction Method, ASTM D7128 – Standard Guide for Using the Seismic Reflection Method, ASCE 7-22 – Minimum Design Loads for Buildings and Other Structures (site classification per Chapter 20), IBC 2024 – Section 1613, site class determination from Vs30, ASTM D4428/D4428M – Crosshole Seismic Testing (for calibration where applicable)

Technical parameters

ParameterTypical value
MethodP-wave refraction / S-wave refraction / SH-wave reflection
Geophone array24 or 48 channel, 5–10 ft spacing
Energy sourceAccelerated weight drop, sledgehammer, or Betsy gun
Typical investigation depth (refraction)50–120 ft below grade
Typical investigation depth (reflection)100–500+ ft below grade
Output parametersVp, Vs, Poisson's ratio, dynamic moduli, layer thickness
Data formatSEG-2 raw files + ASCII velocity profiles + CAD cross sections
Relevant standardASTM D5777 (seismic refraction), ASTM D7128 (MASW/reflection)

Common questions

What's the typical cost range for a seismic tomography survey on an Irving commercial lot?

For most commercial sites in Irving—say a 2- to 5-acre parcel—a combined P-wave refraction and limited reflection survey typically runs between US$2,360 and US$5,190, depending on line length, number of shots, and whether we need a separate S-wave spread. Projects requiring deep reflection profiling with a high-energy source or multiple intersecting lines can push toward the upper end or slightly beyond. Every quote includes mobilization within the DFW metro, field acquisition, processing, and a signed report with interpreted cross sections.

How does seismic tomography compare to MASW for getting Vs30 in Irving?

They complement each other. MASW gives you a 1D shear-wave velocity profile directly below the array center and is fast for site class screening. Seismic refraction tomography gives you a 2D cross section of both P- and S-wave velocity, which picks up lateral changes that MASW smooths over. On a site near the Trinity River, we often run a MASW line for the Vs30 report and a refraction line to map the paleochannel geometry—because the site class alone doesn't tell you about differential settlement potential.

Can you do seismic work on a congested urban site in Irving?

Absolutely, though it takes more planning. On tight lots—think infill development along Belt Line Road or near the Las Colinas urban center—we switch to a smaller geophone spread with 5-ft spacing, use a sledgehammer source instead of the weight drop, and schedule acquisitions on Sundays or early mornings when ambient noise from traffic and HVAC equipment is lowest. We've run clean 12-channel refraction lines in alleyways and parking lots where a drill rig couldn't even set up.

What formations are you typically imaging in the Irving subsurface?

The shallow section in Irving is mostly Quaternary alluvium and terrace deposits overlying the Eagle Ford Shale and Austin Chalk. The Woodbine Formation sits below the Eagle Ford in some areas, and the Ellenburger limestone is the deep competent layer—often at 300 to 500 feet. Seismic refraction resolves the alluvium-to-shale contact and any buried channels within the alluvium. Reflection profiling is what you need to map the Woodbine-Ellenburger interface or to spot karst features in the Austin Chalk that a boring could miss by ten feet.

Location and service area

We serve projects in Irving and surrounding areas.

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