Orlando’s geology is a quiet puzzle of ancient limestone, buried sinkholes, and solution channels hidden beneath the sandy surface. When you place a heavy structure over this kind of karst terrain, the difference between a stable foundation and a costly repair often comes down to knowing the bedrock profile with precision. Seismic tomography — both refraction and reflection — gives our team a non-invasive way to image the subsurface before a single cubic yard of concrete is poured. In a region where the Floridan Aquifer dissolves the carbonate rock from below, relying on scattered borings alone leaves dangerous blind spots. We combine surface-based geophysical lines with targeted geotechnical borings to calibrate velocity models against physical samples, then extend that knowledge across the entire site so you can design with confidence rather than guesswork.
A seismic velocity inversion in a karst setting is not just a number — it is often the first warning that a stable-looking drill log is masking a migration pathway to the surface.
Regional considerations
ASCE 7 Section 20 and Chapter 18 of the IBC make clear that site classification requires reliable shear-wave velocity data — but in Orlando, the real risk is not just a code violation; it is the undetected raveling zone above a paleosinkhole that slowly migrates upward. We have seen sites where standard SPT refusal at 15 feet suggested competent rock, yet a parallel seismic tomography line revealed a 40-foot-deep vertical chimney of loose, water-saturated sand completely missed by the drill rig. The ordinance landscape in Orange County and the City of Orlando increasingly requires geophysical substantiation in sinkhole-prone areas, especially for essential facilities and subdivisions. When tomography is skipped, the owner carries an invisible liability that can surface years later as differential settlement, cracked slabs, or worse — a catastrophic cover collapse during the next heavy rain cycle.
Top questions
How much does a seismic tomography survey cost for a typical Orlando commercial lot?
For a standard 1- to 2-acre commercial site in the Orlando area, a seismic refraction tomography survey with 4 to 6 lines typically falls in the range of US$3,080 to US$4,990, depending on the number of spreads, the depth of investigation required, and the need for combined refraction and reflection. Larger sites with complex karst conditions or the addition of MASW profiles for Vs30 will scale accordingly, and we provide a firm quote after reviewing the site plan and any existing boring logs.
What depth of investigation can seismic refraction achieve in Orlando's sandy soils over limestone?
In the typical profile of Central Florida — loose to medium-dense sands overlying weathered Ocala Limestone — a 24-channel spread with a 10-foot geophone spacing and a sledgehammer source reliably images the top of competent rock to depths of 60 to 80 feet. When we deploy a 48-channel system with a heavier accelerated weight drop, we can push usable refraction data past 100 feet and collect supplementary reflection data reaching several hundred feet to map deeper karst features and the water table interface.
Can seismic tomography distinguish between an air-filled void and a clay-filled sinkhole?
Seismic velocity alone cannot always make that distinction because both air and soft clay can appear as low-velocity zones. On projects where this discrimination matters — such as designing foundations directly over a suspected cavity — we pair the seismic tomography with an electrical resistivity survey on the same alignment. Air-filled voids show high resistivity, while clay-filled zones are conductive, and the combined interpretation gives our engineering team a much clearer diagnostic.
