Free Online SEG-Y Viewer and Seismic Interpretation Tool
| Layer | Vp m/s | Vs m/s | Rho g/cc | Thk m |
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A seismic interpretation workstation that runs in your browser
The tool above does the core of what commercial interpretation software does, with nothing to install and nothing to upload. Open a SEG-Y file, or press Load Demo Line if you do not have one handy, and the section renders on screen with grayscale or red-white-blue density display, a classic wiggle and variable-area mode, adjustable gain, and automatic gain control. From there you can pick up to three horizons with snap-to-peak, let the autotracker follow an event across the whole line, extract the amplitude along any horizon, and export your picks as a CSV. A second tab computes seismic attributes, and the last two tabs hold a full modeling suite: synthetic seismograms, wedge and tuning analysis, exact Zoeppritz AVO, and Gassmann fluid substitution.
Everything happens locally. When you open a .sgy file, JavaScript reads it in your own browser using the FileReader interface; not a single byte travels to any server. That matters because seismic data is often confidential, and it also means the tool is fast: an 80 trace demo line renders instantly and typical 2D lines of a few thousand traces load in seconds.
How to open a SGY file with this SEG-Y viewer
Click the file selector above the section display and choose your file; the extensions .sgy and .segy are both accepted. The parser reads the SEG-Y binary file header for sample count, sample interval, and data format, and supports the two encodings that cover almost all real files: 4-byte IBM floating point (format code 1, the classic tape standard) and 4-byte IEEE floating point (format code 5), plus the integer formats. If the file loads with wrong-looking geometry, the header may use a nonstandard layout; most files written by processing software follow the standard and will open cleanly.
Horizon picking and autotracking
Tick Pick on click, choose a horizon, and click along the event you want to map. Each click snaps to the nearest amplitude peak (or trough, your choice) within a small window, exactly the way workstation snapping behaves, so your picks land on the phase rather than where your mouse happened to be. Autotrack then extends your seed picks trace by trace, following the snapped phase across the line, which turns a dozen clicks into a complete horizon. The amplitude panel below the section updates live, and the CSV export gives you trace number, two-way time, and amplitude for every tracked trace, ready for a spreadsheet or mapping package.
Seismic attributes from the analytic signal
The Attributes tab computes three classic complex-trace attributes using a Hilbert transform built on a fast Fourier transform. Reflection strength (the envelope) shows where the energy is, independent of phase, and is the first place to look for bright spots. Instantaneous phase equalizes strong and weak events, making stratigraphic terminations and subtle unconformities easier to follow. Instantaneous frequency responds to bed thickness and attenuation, the property behind the low-frequency shadows sometimes seen beneath gas.
Synthetic seismograms and the wedge model
The Synthetic + Wedge tab holds a layered earth model with editable Vp, Vs, density, and thickness, plus presets for the standard teaching cases. A Ricker wavelet with a live frequency slider convolves with the reflectivity series to produce the synthetic trace, and the same wavelet drives a sixty-trace wedge model of your reservoir layer thinning from 60 meters to zero. The tuning curve extracted from the wedge shows amplitude brightening to a maximum at the tuning thickness and collapsing below it, with the observed tuning thickness compared against the quarter-wavelength prediction. Drag the frequency slider and watch the tuning thickness move: that is seismic resolution taught in one gesture.
AVO analysis and fluid substitution
The AVO + Fluids tab computes the exact Zoeppritz reflection coefficient at the top of your reservoir layer from 0 to 45 degrees, fits the Shuey intercept and gradient over the usable angle range, and places the result on an intercept-gradient crossplot with the class zones marked. The fluid selector runs Gassmann substitution: your entered reservoir properties are treated as brine-saturated, the dry rock frame is inverted, and brine, oil, or gas cases are reconstructed at the porosity you specify. Watching a Class III anomaly appear as you switch brine to gas, and vanish again with oil, is the entire logic of AVO screening compressed into two clicks.
What this tool is for, and what it is not
This workstation is built for students learning interpretation, geoscientists who need a quick look at a line without a license server, and anyone who has been emailed a .sgy file and simply wants to see it. It handles 2D post-stack data up to a few hundred megabytes. It is not a replacement for full interpretation platforms: there is no 3D volume support, no depth conversion, no well tie against log data, and horizon picks live only until you close the page, so export your CSV before leaving. Within that scope, it is a real interpretation tool, and every number it produces comes from the same published physics as the big packages: Zoeppritz, Gassmann, Ricker, and the analytic signal.
Related Calculators and Reference
- Zoeppritz Equations Calculator for the standalone exact AVO solver behind the gather tab.
- Tuning Thickness Calculator for quick resolution numbers without the full wedge model.
- Gassmann Fluid Substitution Calculator for detailed fluid substitution with custom mineral and fluid moduli.
- Seismic Velocity Converter for the Dix equation and velocity types used in time-depth work.
- AVO Intercept-Gradient Calculator for the Shuey fit on its own.
- External reference: the SEG technical standards page, home of the official SEG-Y format specification.
Common Questions
What is a SEG-Y file?
SEG-Y is the standard exchange format for seismic reflection data: a 3200 byte textual header, a 400 byte binary header, and then one 240 byte header plus samples for every trace. Nearly every seismic dataset ever delivered uses it.
Can I open SEG-Y files online for free?
Yes. The viewer on this page reads standard SEG-Y in your browser, displays the section with gain and color controls, and adds interpretation tools, with no upload and no installation.
Does my seismic data get uploaded?
No. The file is parsed locally in your browser, which is why even confidential data can be viewed safely.