Digitization of BCIS bulletins and the ISC quest to verify pre-digital earthquakes

Abstract

We report on the effort of the International Seismological Centre (ISC, www.isc.ac.uk) to digitise station measurements for earthquakes as well as other types of seismic events that are currently listed in the ISC database without station data. The association of instrumental measurements to a seismic event is fundamental to verify its occurrence and it facilitates, when possible, its hypocentre relocation. We search for relevant station data in the Bureau Central de l’Association Internationale de Sismologie (BCIS). The BCIS bulletins were produced at the same time of the International Seismological Summary (ISS) but they appear to list more events with data than the ISS from the 1950s. Unfortunately, BCIS bulletins have not been digitised in a systematic way. We show that during the period going from the mid-1950s up to 1963 the BCIS is a unique source of station data that allowed us to verify thousands of earthquakes worldwide and significantly expand the global record of seismicity in those years. The data digitised in this work will play a key role in future works regarding earthquakes in the pre-digital era.

Keywords

• Digitisation
• Phase arrival times
• Seismic stations
• Earthquake parameters
• Bulletins