GCF2SAC 1.4.6

GCF2SAC is a command line utility for converting GCF data to SAC format.

Note: GCF2SAC will only process data for a single stream (i.e. a single component at a single sample rate from a single instrument). If you wish to convert a file containing multiple streams, you should pre-process it using GCFSPLIT and then convert the resulting files one by one.


GCF2SAC v1.4.6 for Windows (80K .zip)


GCF2SAC v1.4.6 for macOS (123K .gz).


GCF2SAC v1.4.6 for Linux i386 (86K .gz).

Note: The Linux binary needs access to the Qt runtime library (2.4M .gz), either in your normal library path or in the current directory.
Note: This 32-bit Linux software runs on 32-bit and 64-bit operating systems. To install it on a 64-bit Linux platform, please follow these instructions to install the relevant libraries.


To get a list of the options, run the gcf2sac program without any parameters. The following text is displayed:

GCF2SAC      v1.4.6    (c) Guralp systems 2018
Converter for GCF to SAC format
Usage: GCF2SAC gcffile [-l] [-o:output_dir]
    -l produces little-endian (intel) byte order (default big-endian)
    "output_dir" specifies a directory for converted files. If not specified,
            the directory of the input file is used.

  An output file of the same name with extension '.sac' is generated.
  Any gaps in the time-series will be filled with value -2147483647
  Any blocks with a timestamp going backwards will be ignored.
  The input GCF file should contain data for one stream only.

You can use wildcards in the file-name, so gcf2sac *.gcf will convert every GCF file in the current directory. The name of the converted file will be the same as the GCF file name, with the extension changed to .sac.

SAC files do not support data which are not in time sequence. GCF2SAC will fill in any gaps with a dummy value (231-1). If data are encountered with time-stamps earlier than the latest so far received, GCF2SAC will discard them.

Because of this, back-filling transmission modes (such as the DM24′s ADAPTIVE mode) will only work as expected if the data are put in order before being saved as a GCF file. This can be done in Scream! using a suitably large stream buffer or by using the gcfrepair tool.

You can configure Scream! to run GCF2SAC automatically on GCF files it produces by setting it as a post-processor. Although Scream! can output SAC files, it will not output in multiple formats simultaneously, so using GCF2SAC as a post-processor will save you running two copies of Scream!.

To set a post-processor, open the Files tab of Scream!’s Setup window and enter the full path of the GCF2SAC program file in the Post-Processor box. Click the OK button to save the setting.

The -l option

Including the -l option in the command line will force GCF2SAC to use little-endian (Intel) byte order. The default is big-endian (Motorola, or ‘network’) byte order.

The -o: option

Supplying a directory path name after -o: will make GCF2SAC place all converted files in this directory. If the directory does not exist, it will be created.

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