The Bulletin of the International Seismological Centre is the primary output of the ISC and is regarded as the definitive record of the Earth's seismicity.

The ISC Bulletin contains data from 1900 to present day (2025-06-30). The Reviewed ISC Bulletin, which is manually checked by ISC analysts and relocated (when there are sufficient data) is typically 24 months behind real-time and is currently up to 2023-07-01.

The ISC Bulletin may be accessed in one of three ways:

• using the online web searches, which provides access to all ISC Bulletin data;
• using a web services client to access and search ISC Bulletin data;
• download monthly files (ISF or pdf) of the Reviewed ISC Bulletin from the ISC ftp (via http) site;
• access it via the FTP protocol (using FTP software) manually from ftp.isc.ac.uk

Creation of the ISC Bulletin

The ISC Bulletin relies on data contributed by seismological agencies from around the world. These data, which may include hypocentres, phase arrival-times, focal mechanism solutions, etc. are automatically grouped into events, which form the basis of the ISC Bulletin. An automatic thresholding process decides whether each event should be manually reviewed by an ISC analyst/editor, which will also be relocated by the ISC, depending on the available data.

The main features of the event grouping are:

• Score hypocentres from the phase data used to locate them (azimuthal and secondary azimuthal gap, distance range, network distribution, number of stations, number of phases, etc);
• Compare the hypocentre location and origin time with similarly located hypocentres;
• Group, split or create new events based on the hypocentre score and the hypocentre parameter comparison.