THE 1998 ANNUAL SUMMARY OF THE ISC BULLETIN

Conclusions

1. The 1998 ISC Bulletin remains the most comprehensive global source of seismic parametric data. The overall mb completeness threshold is found to be as low as 4.0, although the ISC mb values are negatively biased comparing to those of NEIC.

2. 75% of the ISC events above completeness threshold are located based on station readings from at least two networks.

3. The ISC Bulletin events generally have smaller station azimuthal gap than those of NEIC or EIDC (GSETT-3).

4. The use of phases other than P is needed to improve locations of some events above the completeness threshold.

5. NEIC, EIDC, China and Nepal contribute about 95% of all body wave amplitudes. The ISC would benefit from other agencies contributing amplitudes more often.

6. The number of events discovered by the ISC, based on unassociated station reports, declines as more comprehensive local reports are received.

7. The ISC would benefit from station reports contributed as associated to known hypocentres, if at all possible.