Automated event location by seismic arrays and recent methods for enhancement

This paper describes procedures to locate seismic events at regional distan ces by single seismic arrays. First it reviews the methods used for interac tive analysis and compares their performance using array data to that of si ngle three-component stations. Then the paper focuses on automated location . Ten days of continuous-operation ARCESS data are analyzed. They are evalu ated by standard NORSAR routines of beamforming and f-k analysis, and by a complementary, independent approach. This approach utilizes pattern recogni tion (PR) and rule-based system (RBS) techniques to derive an automated bul letin from a subset of four array stations. The content of both lists, i.e. , the ARCESS log of NORSAR and the new, PR-based list, are combined to form a joint bulletin. Its enhanced quality is achieved by rules for consistenc y check or "pluralistic reasoning."