Relocation of microearthquakes in Beijing and its northwest neighbouring area

Ｒｅｌｏｃａｔｉｏｎ　ｏｆ　ｍｉｃｒｏｅａｒｔｈｑｕａｋｅｓ　ｉｎ　Ｂｅｉｊｉｎｇ　ａｎｄ　ｉｔｓ　ｎｏｒｔｈｗｅｓｔ　ｎｅｉｇｈｂｏｕｒｉｎｇ　ａｒｅａＳｕ－ＹｕｎＷＡＮＧ（汪素云）；Ｚｈｏｎｇ－ＨｕａｉＸＵ（许忠淮）；Ｙａｎ－ＸｉａｎｇＹＵ（俞言...

Relocation of microearthquakes in Beijing and its northwest neighbouring area

This study relocated 348 microearthquakes which occurred in Beijing and its northwest neighbouring area (39° – 41°N, 114° – 117°E) during 1979–March of 1992. In the relocation the Powell searching technique was used and the associated error of earthquake hypocenters was estimated by numerical tests. Precision of hypocenter locations is improved by rechecking and supplementing readings of arriving times of the seismic phases used, testing and selecting appropriate crustal model, and modifying the computer program. The overall averageRMS residual of arriving times has been reduced to 0.45 s from the previous value of 0.80 s. For nearly 10 per cent of the relocated hypocenters, which are mostly in border region of the area covered by the Beijing Telemetered Seismic Network, have been shifted more than 10 km. After the relocation the number of earthquakes with focal depth determination has been increased to 313 from the previous 132. Contribution 94A0001 of Institute of Geophysics, SSB, China. This study was a subproject, numbered 85-907-04-01-02-03, of the 8th five-year research program of the State Seismological Bureau (SSB), China. Contribution 94A0001 of the Institute of Geophysics, SSB.