新的震级国家标准在2018年陕西宁强MS 5.3地震震源参数测定中的应用

利用国家测震台网记录到的2018年9月12日陕西宁强M_S 5.3地震的波形数据,使用新震级国标计算了此次地震宽频带面波震级M_(S(BB)),利用CAP波形反演方法得到震源机制解及矩震级M_W。结果显示:利用50个宽频带测震台站的波形数据测得此次地震的M_(S(BB))为5.0,与GCMT测定的M_S震级一致;由CAP方法反演得到的最佳双力偶参数为节面Ⅰ:走向169°/倾角81°/滑动角9°,节面Ⅱ:走向78°/倾角81°/滑动角171°;矩震级M_W为5.0,与USGS公布的结果较一致,与GCMT公布的结果仅差0.1。研究认为,此次地震震级应为5.0左右,在日常地震速报中可将M_W作为首选发布震级;而对于中强地震,M_(S(BB))震级相较于M_S震级作为发布震级更为合理。

Application of the new national magnitude standards in the determination of focal parameters of the 2018 Ningqiang MS 5.3 earthquake in Shaanxi Province

Based on the waveform data of the M_S 5.3 earthquake of September 12, 2018 in Ningqiang County, Hanzhong City, Shaanxi Province recorded by the National Seismological Network, this paper calculates the broadband surface wave magnitude M_S(BB) of the earthquake by using the new magnitude national standard, and obtains the focal mechanism solution and moment magnitude M_W by using CAP waveform inversion method. The results show that the M_S(BB) of this earthquake is 5.0 by using the waveform data of 50 broadband seismic stations, which is consistent with the M_S magnitude measured by GCMT. The two nodal planes of the best double couple solution by using CAP waveform inversion method are:for the nodal planeⅠ strike 169°/dip 81°/slip 9?nd strike 78°/dip 81°/slip 171° for the nodal plane Ⅱ; and the moment magnitude is M_W 5.0, which are consistent with the results measured by USGS. The difference between the results of M_W by CAP inversion and GCMT published is only 0.1. We believe that the magnitude of this earthquake should be about 5.0. Therefore, M_W is the preferred magnitude issued in daily earthquake quick report. For moderate and strong earthquakes, M_S(BB) is more reasonable than M_S in publishing magnitude.