What this SAC audit checks
The Seismic Analysis Code (SAC) binary format has a 632-byte header, followed by one or two float32 data sections. This tool detects byte order from the version field, reads common timing, station, event, and sample-count fields, checks the payload length implied by NPTS and file type, scans the first section for non-finite values and observed min/max/mean, and compares them with declared summary fields.
Version 7 and timing
SAC v7 adds a 176-byte footer with 22 double-precision values. The report checks its presence and compares defined footer values with header floats. For evenly spaced time-series data, it checks that E approximately matches B + (NPTS−1)×DELTA. An absolute UTC span is shown only when the reference-time fields and B/E are available.
Validation boundary
This is a bounded binary preflight, not a complete SAC validator or seismic interpretation package. It does not calibrate instrument response, identify seismic arrivals, verify phase picks or event origin, resolve all SAC enumerations and optional fields, validate physics, or convert data. It supports common v6/v7 ITIME, IRLIM, IAMPH, and IXY layouts, but not alphanumeric SAC or unsupported IFTYPE layouts. Check scientific results with SAC or another trusted seismology tool.
Frequently asked questions
Does this upload my waveform?
No. The file is read and analyzed in your browser only.
Why can a file have two data sections?
Unevenly spaced time series, spectra, and XY files can carry a second independent-variable or paired-component array. The size check accounts for that array; the amplitude summary applies only to the first section.
Why can header and footer values differ slightly?
The v6-style header stores float32 values while the v7 footer stores float64 values. Small differences are expected from precision; this page warns only about larger discrepancies.
Authoritative reference
See the IRIS SAC Data File Format manual for the binary header, data sections, undefined markers, field meanings, and v7 footer.
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