The IRIS DMC provides data to users in several different formats.
This is a format defined by the SAC software suite, although it is supported by many other tools at this point. This is widely used and makes a good starting point for data processing tasks.
The SAC data format itself includes only waveform data; it is usually accompanied by separate metadata files in Poles and Zeros (SACPZ) format.
The Standard for the Exchange of Earthquake Data (SEED) is a data format intended primarily for the archival and exchange of seismological time series data and related metadata.
SEED is designed for archival rather than processing, so most use cases should use a different format like SAC.
MiniSEED is a stripped down version of SEED containing only waveform data. There is no station and channel metadata included.
Dataless SEED ¶
A dataless SEED volume is the metadata counterpart to miniSEED. It contains only station and channel metadata, without any time series values.
Simple ASCII ¶
This is a simple text-based data format, suitable for importing into a spreadsheet or other tool where specialized data parsing is not available or required.
Note that this is a very simple format, and is not well suited for serious data processing.
This is very similar to the Simple ASCII format, but includes some additional metadata and conforms with a well-defined standard.