地震学报Issue(6)：983-996,14.DOI:10.11939/jass.2015.06.009
2013年四川芦山 MS7．0地震自动速报震级偏差分析及方法改进
Analysis on magnitude deviation of the 2013 Lushan,Sichuan, MS7.0 earthquake from Automatic Earthquake Location and Report System and its improvement
摘要
Abstract
The procedure of automatic determination of magnitude for the 20 April 2013,Lushan MS 7.0 earthquake is roughly reproduced by using the wave-forms from 40 stations within epicentral distance of 320 km in this paper.The results demonstrate that the magnitude is rising quickly when the parameters of this earthquake were issued by China Earthquake Administration (CEA).At the moment,the measured standard magnitude M5.8 is consistent well with the M5.9 announced by CEA at almost the same time,but it is much smaller than M7.0 revised by the analyst later.The magnitude determined by Automatic Earthquake Location and Report System deviates largely,and the reasons are:① The usage of clipped records underestimated the magnitude;② Rapidness is emphasized and the accuracy is neglected.S (or Lg)wave is absent at some stations when the earthquake parameters are issued,resulting in the magnitude smaller.Therefore,by reducing the effect of clipped records within a proper epicentral range and delaying some seconds,the magnitude will be 6.8 at 137 s after occurrence of the earthquake.Additionally,the determination method of MWP is applied and MW 6.8 is available at 77 s after the earthquake,suggesting the determination method of MWP can be applied to get a stable moment magni-tude rapidly.Finally,we propose the following measures for improving the method for magnitude determination by Automatic Earthquake Location and Report System.① The determination method of ML is used for the events with magnitude less than 7.0.In this case,ML should be determined with seismo-grams without clipped records,selected from the stations within a proper epicentral range in an area where the number of seismograms without clipped records is absolutely predominant.Meanwhile,the determination method of ML should be delayed until the furthest station receives the maximum amplitude of S (or Lg)wave.② The method for the MWP determination is able to be applied to determine the moment magnitude for large earthquakes.关键词
芦山 MS 7.0 地震/地震自动速报/震级测定方法/ML/MWPKey words
Lushan MS 7.0 earthquake/Automatic Earthquake Location and Report System/magnitude determination method/ML/MWP分类
天文与地球科学引用本文复制引用
梁建宏,孙丽,徐志国,刘杰..2013年四川芦山 MS7．0地震自动速报震级偏差分析及方法改进[J].地震学报,2015,(6):983-996,14.基金项目
地震科技星火计划项目（XH15048）和经常性项目“国家自动速报中心（CSN／GSN）运维及系统优化”共同资助． （）
