MATLAB Code Implementation for Seismic Data Reading

Reading SEGY format seismic data in MATLAB is a common task in seismic exploration and geological research. SEGY (Standard Exchange Format for Seismic Data) is a widely-used binary format for storing seismic data records, typically containing survey line information, sampling point data, and related metadata. SEGY File Structure SEGY files generally consist of three parts: file header, trace headers, and data section. The file header contains global information such as sampling rate and number of traces; trace headers record parameters for each data trace like coordinates and timing; the data section stores actual seismic waveform data. MATLAB Implementation Approach Binary File Reading: Since SEGY is a binary format, MATLAB's `fopen` and `fread` functions can be used to read file content byte by byte. The implementation typically involves opening the file with proper endian specification (e.g., `'b'` for big-endian or `'l'` for little-endian) using `fopen(filename, 'r', endianFormat)`. File Header Parsing: The first 3600 bytes usually contain text or binary file headers recording information like sample interval and data format (IBM floating-point or IEEE floating-point). Implementation requires parsing these headers according to SEGY standards using `fread` with appropriate precision parameters. Trace Header Processing: Each trace is preceded by a 240-byte trace header containing metadata such as trace sequence number and coordinate information. Code implementation involves reading these headers sequentially using `fread(fid, 60, 'int32')` or similar commands based on the header format. Data Section Reading: Based on the format specified in the file header (e.g., 4-byte floating-point numbers) and total trace count, data is read trace by trace and stored in matrices for subsequent analysis or visualization. A typical implementation uses loops with `fread(fid, nsamples, 'float32')` where nsamples is determined from header information. Important Considerations Byte Order: SEGY files may use big-endian or little-endian storage, requiring correct specification using `fopen`'s machine format parameter. Code should include automatic endianness detection or user specification. Data Scaling: Some SEGY files apply scaling factors to data values, which must be restored during reading. Implementation needs to check scaling coefficients in trace headers and apply appropriate corrections. Efficiency Optimization: For large seismic datasets, reading traces sequentially rather than loading the entire file at once prevents memory issues. This can be implemented using partial reading techniques with careful file positioning via `fseek`. Through this workflow, MATLAB can flexibly parse SEGY files, providing fundamental support for seismic data processing tasks such as filtering and migration imaging. The implementation typically results in structured data outputs compatible with MATLAB's seismic processing toolbox functions.