The Collected Bulletin is data in the form closest to that contributed to the ISC. Contributed hypocentres are not grouped into ISC-defined events. Only the phase readings associated with a hypocentre in a report from a contributor are shown. The phase identifications, travel time residuals and other data on how phase arrivals relate to the hypocentre are just as reported to the ISC. Data for the collected Bulletin are available from from 1 Jan 1999 and newly contributed data are available promptly after they are received at the ISC.

The Published Bulletin is data from the printed Bulletin. The prime hypocentre, body wave magnitude and surface wave magnitude for events recorded teleseismically are computed by the ISC using procedures, travel times, and attenuation curves that are consistent all around the world. Phase readings from all reports contributed to the ISC are associated with the prime hypocentres. Phase identifications and travel time residuals are the result of calculation and thorough review by ISC seismologists. Data are available for the published Bulletin from 1 Jan 1964 and ISC review generally is completed 20 to 22 months after events occur.

The Comprehensive Bulletin is the most complete set of data. It includes all of the information in the published Bulletin, plus

• contributed data on events too small to warrant ISC re-analysis
• contributed data on events from months not yet analysed at the ISC
• data contributed to the ISC too late for the published Bulletin
• corrections where the ISC has learned of errors in the published Bulletin

For events not in the published Bulletin, the comprehensive Bulletin includes results from automatic processing at the ISC. ISC processing includes grouping of hypocentres that are probably different estimates for the same event and association of each phase reading with the event that it fits "best".