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Rebuild of the Bulletin of the International Seismological Centre (ISC)

Session: Overdue?

Type: Oral

Date: 4/21/2021

Presentation Time: 10:30 AM Pacific

Description: 

The International Seismological Centre (ISC) produces the Bulletin which is regarded as the most long-term, comprehensive and homogeneous catalogue of instrumentally recorded seismicity on a global scale, primarily based on seismic bulletins from ~150 seismic networks worldwide. The Bulletin is used in a wide range of geophysical studies. Users benefit from the most comprehensive set of measurements from the majority of permanent networks and uniformity of included event parameters. The Bulletin also serves as a foundation for specialised derivative datasets such as the ISC-GEM catalogue, ISC-EHB dataset, IASPEI GT-List and ISC Event Bibliography.

Despite a strict approach to preserving the operational procedures over the last ~50 years, changes are inevitable to achieve the best possible accuracy of earthquake parameters. The last fundamental change in procedures has affected the data years 2011 and beyond (Bondár and Storchak, 2011). This is why we had to rebuild the earlier part (1964-2010) to achieve compatibility in earthquake hypocentres and magnitudes through its entire period.

We announce that the entire reviewed part of the ISC Bulletin (1964-2018) is now based on the same 1D velocity model, ak135, and the same earthquake and magnitude computation procedures. We give an account of notable changes in the bulletin from the removal of poorly constrained events to the addition of many small events, based on additional reports from permanent and temporary seismic deployments. As a result, the rebuilt ISC Bulletin has 17% more seismic arrival times from 21% more stations. The rebuilt mb is on average larger than the original mb by only 0.05 unit of magnitude. The rebuilt MS is only 0.01 units larger than the original (Storchak et al., 2020). Another important feature was an inclusion of ~12,000 ISC source mechanisms based on reported first motion polarities (Lentas, 2018).

Presenting Author: Dmitry A. Storchak

Student Presenter: No

Authors