用余震作为经验格林函数从GDSN长周期波形资料中提取1999年集集地震的震源时间函数  

SOURCE TIME FUNCTIONS OF THE 1999, Jiji(Chi-Chi) EARTHQUAKE FROM GDSN LONG PERIOD WAVEFORM DATA USING AFTERSHOCKS AS EMPIRICAL GREEN′S FUNCTION

作　　者：许力生[1] G.Patau 陈运泰[1] 

机构地区：[1]中国地震局地球物理研究所,中国北京100081 [2]法国巴黎地球物理研究所,法国巴黎75252

出　　处：《地震学报》2002年第2期113-125,共13页Acta Seismologica Sinica

基　　金：国家自然科学基金 (4 990 40 0 4);法国巴黎地球物理研究所资助

摘　　要：1999年 9月 2 0日 17h 4 7minUTC(北京时间 9月 2 1日 0 1h 4 7min)中国台湾省南投县集集镇发生MW7.6地震 ,随后又发生许多中强余震 .我们从这些余震中选择了MW6 .1和MW6 .2两次余震分别作为经验格林函数 ,并从包括IRIS ,GEOSCOPE和CDSN在内的全球数字地震台网的长周期波形资料中提取了主震的震源时间函数 .对于发生在 9月 2 2日的MW6 .1余震 ,有 2 6个台站的 78条记录的 97对震相清晰可用 ;对于发生在 9月 2 5日的MW6 .2余震 ,有 2 4个台站的 72条记录的 81对震相清晰可用 .对于每个台站 ,从P和S两种震相中提取震源时间函数 ,分别称之为P波震源时间函数和S波震源时间函数 .这样 ,利用两次余震从长周期波形资料中共提取了 178个震源时间函数 .从这些震源时间函数可以看到 ,除在特殊方位的几个震源时间函数由于主震和余震的震源机制的差别引起较大的畸变外 ,大多数台站的震源时间函数都具有相似性 ;同时 ,其形状随方位发生一定程度的变化 .这两种特征都是对所提取的震源时间函数的稳定性和可靠性的客观反映 .通过分析确认 ,这次地震由两次子事件构成 ,总持续时间约 2 6s .第二次事件比第一次事件晚大约 7s ,第一次事件的矩释放率比第二次事件大 15 % .A large earthquake (M W=7.6) occurred in Jiji(Chi-Chi), Taiwan, China on September 20, 1999, and was followed by many moderate-size shocks in the following days. Two of the largest aftershocks with the magnitudes of M W6.1 and M W 6.2, respectively, were used as empirical Green′s functions (EGF) to obtain the source time functions (STFs) of the main shock from long-period waveform data of the Global Digital Seismograph Network (GDSN) including IRIS, GEOSCOPE and CDSN. For the M W6.1 aftershock of September 22, there were 97 pairs of phases clear enough from 78 recordings of 26 stations; for the M W6.2 aftershock of September 25, there were 81 pairs of phases clear enough from 72 recordings of 24 stations. For each station, 2 types of STFs were retrieved, which are called P-STF and S-STF due to being from P and S phases, respectively. Totally, 178 STF individuals were obtained for source-process analysis of the main shock. It was noticed that, in general, STFs from most of the stations had similarities except that those in special azimuths looked different or odd due to the mechanism difference between the main shock and the aftershocks; and in detail, the shapes of the STFs varied with azimuth. Both of them reflected the stability and reliability of the retrieved STFs. The comprehensive analysis of those STFs suggested that this event consisted of two sub-events, the total duration time was about 26 s, and on the average, the moment-release rate of the second event was about 7 s later than that of the first one, and the first event was stronger by about 15% than the second one.

关 键 词：集集地震 长周期波形 震源时间函数 经验格林函数 余震 

分 类 号：P315.3[天文地球—地震学]