Earthworm Auto-Earthquake Location Performance and Recent Improvements in Seismic Data Acquisition, Processing, Archiving and Dissemination at Kandilli Observatory and Earthquake Research Institute

Abstract

The Kandilli Observatory Real-Time Automated Seismic Data Processing System (KORTASDPS) has been one of the most important infrastructure developments in the last 5 years at Kandilli Observatory and Earthquake Research Institute (KOERI), Bogazici University. KORTASDPS uses the Earthworm (EW) software suite for its real-time processing of seismic data. Primary functions of EW are to serve as real-time data server and auto-detect and locate earthquakes. Performance evaluation of EW was done by comparing its hypocenter catalogs from years 2004 and 2005 with catalogs produced by the National Earthquake Monitoring Center (NEMC) which relies on manual detection and location techniques. In general EW performance is highest in northwest Turkey where station density and relative station sensitivity are high. Catalog correlations reveal that this area has an estimated 3.1 low magnitude threshold for a 90% earthquake auto-detection and location reliability. For the rest of the country this low magnitude threshold estimate ranges between 4.4 and 4.6. Three points have been proposed to improve EW auto-detection and location accuracy. These are more accurate timing of emergent phases, use of reliable S phases and an increase in the effective seismic network density with more sensitive and reliable stations. Already expansion and modernization of KOERI’s seismic network in 2004 and 2005 have resulted in clear improvements in EW’s auto-detection and location performance. A one month pilot analysis was made to understand the nature of the consistent large numbers of EW cataloged seismic events that do not correlate with NEMC. Results show that after careful manual relocation of these events that the majority are not found in either NEMC’s preliminary or final catalog and that these events represent almost one third of all events found in the combined EW and NEMC catalogs. Since 2003 the KOERI re-designed digital broadband network has increased from 4 to 33 stations and international shared broadband stations from 2 to 10. The past and planned increases of more sensitive and higher quality seismic stations has and will continue to improve the performance of EW’s auto-detection and location reliability and provide a source of information rich data to be used for ongoing and future seismological research.