Rebuild of the Bulletin of the International Seismological Centre (ISC), part 1: 1964–1979

Abstract

The data from the Bulletin of the International Seismological Centre (ISC) have always been and still remain in demand for a wide range of studies in Geosciences. The unique features of the Bulletin include long-term coverage (1904-present), the most comprehensive set of included seismic data from the majority of permanent seismic networks at any given time in the history of instrumental recording (currently ~ 150) and homogeneity of the data and their representation. In order to preserve this homogeneity, the ISC has followed its own standard seismic event processing procedures that have not substantially changed until the early 2000s. Several considerable and necessary advancements in the ISC data collection and seismic event location procedures have created a need to rebuild the data for preceding years in line with the new procedures. Thus was set up a project to rebuild the ISC Bulletin for the period from the beginning of the ISC data till the end of data year 2010. The project is known as the Rebuild of the ISC Bulletin. From data month of January 2011, the ISC data have already been processed with the fully tested and established new procedures and do not require an alteration. It was inconceivable even to think about such a project for many tens of years, but great advances in computer power and increased support by the ISC MemberInstitutions and Sponsors have given us a chance to perform this project. Having obtained a lot of experience on the way, we believe that within a few years the entire period of the ISC data will be reprocessed and extended for the entire period of instrumental seismological recordings from 1904 till present. The purpose of this article is to describe the work on reprocessing the ISC Bulletin data under the Rebuild project. We also announce the release of the rebuilt ISC Bulletin for the period 1964-1979 with all seismic events reprocessed and relocated in line with the modern ISC procedures, ~ 68,000 new events, 255 new stations, ~ 815,000 new seismic phases, more robust and reliable mb and M S magnitude evaluations and the addition of ~ 2700 new M S magnitudes.

The ISC-GEM Earthquake Catalogue (1904–2014): status after the Extension Project

“…The number of stations reporting amplitudes increased until World War II, dropped in the 1940s and improved significantly from 1953. European and many Russian stations are the most important contributors to amplitude readings compared to stations in other continents, except for La Paz (LPZ, Observatorio San Calixto, Bolivia) and Riverview College (RIV, Sydney, Australia) from the Jesuit seismic network (Udías and Stauder, 1996). The number of stations per event contributing amplitudes ranges from 0 to above 40, with the median per year oscillating from 0 to 6 ( Fig.…”

The ISC Bulletin as a comprehensive source of earthquake source mechanisms

“…Here we use a unique agency code for these source mechanisms and replace the HRVD agency code with the GCMT code throughout the ISC Bulletin. This is already done for the time period 1976-1979 covered by the first part of the ISC rebuild project (1964( -1979( , Storchak et al, 2017. After completion of the ISC rebuild project, all remaining HRVD source mechanism solutions will be available under the GCMT code.…”

“…Since then new focal mechanisms have routinely been added for every data month added in the Reviewed ISC Bulletin. Moreover, we have published focal mechanism solutions obtained from reported polarities for the ISC-relocated earthquakes (m ISC b > 3.5) covering the time period 1964-1984 as part of the rebuild project (Storchak et al, 2017) and focal mechanism solutions obtained from reported polarities in the ISS Bulletins (see http://www.isc.ac.uk/ projects/focalmechs/, last access: April 2019). The gap currently shown in Fig.…”

Untitled

“…The data is sent to the user's e-mail as mini-seed, full-seed or dataless (SEED File). (Storchak et al, 2017). Figure 6.1 compares the ISC locations before and after the Rebuild project for the entirety of the released rebuilt ISC Bulletin from 1964 to 1990.…”