国际监测系统(IMS)对内华达地区地震事件的检测和定位能力分析

摘要

A comparison study between the Seismic Event Bulletin produced by ANSS and IDC was carried out to evaluate the detection and location capability of IMS for seismic events occurred in Nevada, USA, and the main factors affecting the detection were analyzed. The result shows that IMS can detect minimum earthquakes of mb2. 1 occurring in Nevada. IMS can detect all events of M>4. 5. More than 80% of M>4. 0 events in ANSS SEB are also detected by IMS. The epicenters determined by IDC are averagely about 13. 6 kilometers away from the epicenters determined by the ANSS using local/regional seismic station networks, with the largest deviation of 82 km. Comparing different magnitudes of the same events shows that there is a linear relationship between rnthe body wave magnitude mb determined by IDC and M determined by ANSS. Furthermore, the former is averagely lower than the latter by about 0. 2 magnitude unit. The factors that may contribute to the relative location deviation were statistically studied. The result suggested that number of defining phases and azimuth gap in IDC REB contributes most to this relative deviation, but the minimum event-station distance has little effect on relative deviation.%通过对国际数据中心(IDC)审议地震公报(REB)与美国先进的国家地震系统(ANSS)地震目录的比较,分析了国际监测系统(IMS)对美国内华达地区地震事件的检测和定位能力,以及影响监测结果的主要因素.结果表明,对内华达地区的地震事件,IMS最低可检测mb为2.1的地震事件.对M＞4.5的地震事件,IMS可以全部检测；对M＞4.0的地震,IMS的检测概率超过80％.相对定位误差分析表明,IDC REB相对于ANSS地震目录的平均相对定位误差为13.6 km,最大相对误差为82 km.共同事件的震级拟合表明,ML(ANSS)与mb (IDC)之间具有明显的线性关系,且mb (IDC)平均比ML (ANSS)低0.2个震级单位.统计分析表明,定义震相数和定位台站空隙角对定位误差的影响较大,而最小震中距的影响不明显.