Pdif波在中国CDSN台站的运动学特征  

The Kinematic Characteristics of Pdif-waves at CDSN Stations

作　　者：许健生[1,2] 隗永刚[1,2] 张淑珍 

机构地区：[1]中国地震局地球物理所北京地震台,北京100095 [2]北京白家疃地球科学国家野外科学观测研究站,北京100095 [3]甘肃省地震局兰州观象台,甘肃兰州730046 [4]兰州地球物理国家野外科学观测研究站,甘肃兰州730046

出　　处：《地震工程学报》2013年第3期610-617,共8页China Earthquake Engineering Journal

基　　金：中国地震局地球物理研究所中央级公益性科研院所基本科研业务专项项目(DQJB11B07)

摘　　要：利用中国数字地震台网(简称CDSN,下同)11个台的宽频带长周期(VLP)数字记录对1990-2012年间的124个极远震记录进行了分析处理,在震中距100.0°～179.0°之间,获取了CDSN11个台站的Pdif波的震相数据,得到了Pdif波在地球核幔界面上衍射的运动学特征和《Pdif波走时表》。所得结果大大拓展了Pdif的记录范围,在144.0°～179.0°之间弥补了《IASPEI1991地震波走时表》的缺失,为更大范围内的Pdif震相分析提供了参考标准,有助于提高中国地震台网的地震分析水平和积累震相分析经验,以及对地球核幔边界物理性质的认识。The traveling-time curve of the P-wave ends at an epicentral distance （△） of about 100°.At epicentral distances larger than 100° （△〉100°）,P-waves pass through the core-mantle boundary （CMB） and start to be diffracted around the core with speeds of ～13.7 km/s.The diffracted wave is termed Pdif.Due to the sharp decrease of the P-wave velocity at the core-mantle boundary from 13.7 km/s to ～8.0 km/s,the short period P-wave is strongly refracted into the core with speeds of ～8.0 to 11.2 km/s.This refracted wave is termed PKP （PKPab,PKPbc and PKPdf）.The Pdif wave was first recognized on seismogram by Denmark seismologist Lehmann in 1936.The traveling-time curve of the Pdif wave was well defined at distances of 105° to 130° by seismologists Jeffres and Bullen in 1940,using the seismic data from 1930 to 1940,for earthquakes with depths from 33 to 794 km.In 1991,the traveling-time curve of the Pdif wave was updated by Kennett[6] for distances of 100° to 144° and depths of 0,100,300,and 600 km using seismic data from 1964 to 1987.In the China Digital Seismograph Network （CDSN）,the Pdif wave of strong earthquakes,whose distances range from about 100.2° to 179.0°,may be observed so that the Pdif phase can be analyzed perfectly.We collected and analyzed 124 broad-band seismic recordings at the 11 CDSN stations during a period of 1990 to 2012,from very-far-field events with magnitudes of ～6.0to 8.8 and depths ～4 to 631.3 km.The kinematic characteristics of the Pdif phase are summarized as the following：（1） There is a good linear relationship between traveling-times and distances,and a systematic bias exists between our results and those of the IASPEI 1991 table; for example,the difference reaches 11.2 s at △=100°,and 17.0 s at △=144°.（2） For △〉100°,the Pdif arrival time is about 4 min and 10.7 s to 29.8 s earlier than the PKP wave,and the time difference between the Pdif and PKP waves with distance could be formulated as：TPKP Pdif =-2.835△＋550.7 （h ≤ 1

关 键 词：极远震 Pdif波走时表 运动学特征 中国数字地震台网(CDSN) 

分 类 号：P315.31[天文地球—地震学]