Free Online SEGY Header Inspector: Read Seismic File Headers

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The inspector decodes the 3200 byte EBCDIC textual header, reads the key binary header fields, and estimates the trace count from the file size. Only the headers are read, so even multi gigabyte files inspect instantly. Nothing is uploaded anywhere.

Thirty seconds that save an afternoon

Half of all seismic loading problems are header problems: a format code the software guessed wrong, a sample rate nobody checked, a processing history buried in text nobody read. The inspector above opens any SEGY file and shows you everything before you commit to loading it. The 3200 byte textual header is decoded from EBCDIC into readable text, the binary header fields are extracted and named, and the trace count is checked against the file size, which instantly exposes nonstandard files. A built in demo file shows the layout if you have no SEGY at hand.

A SEGY seismic file opened to show its EBCDIC textual header and decoded binary header fields including sample interval, samples per trace, and format code
The textual header tells the story; the binary header tells the software what to expect.

Only the headers are read, so files of any size inspect instantly, and nothing uploads anywhere: the file stays on your machine from first byte to last.

What each field tells you

  • The sample interval and samples per trace give the trace length in seconds, the first thing to compare against what the acquisition report claims.
  • The format code decides how every amplitude is decoded: IBM float and IEEE float differ silently, and reading one as the other produces garbage that almost looks like data.
  • The size check divides the file into traces: when it does not come out whole, the file has extended headers or nonstandard records, and knowing that early changes how you load it.
  • The textual header is where processors leave their story: filters applied, datum, replacement velocity, and the line name that proves you were sent the right file.

What this inspector is for

Checking deliveries before loading them, diagnosing files the workstation rejects, and teaching the SEGY layout with a synthetic file you can regenerate at will. When the headers check out, the seismic viewer on this site takes the file from here.

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