地震研究

2007年宁洱6.4级地震横波分裂研究^*

毛慧玲,秦嘉政

(云南省地震局,昆明 650224)

关键词：横波分裂; 裂隙各向异性; 延迟时间; 宁洱地震

Study on the Shear-wave Splitting of the 2007 Ning'er, Yunnan,M_S6.4 Earthquake Sequence

MAO Hui-ling,QIN Jia-zheng

(Earthquake Administration of Yunnan Province,Kunming 650224,Yunnan,China)

Keywords：shear-wave splitting; extensive dilatancy anisotropy; delay time; Ning'er earthquake

备注

收稿日期:2010-01-04
基金项目:云南省十项措施“云南强震活动与板缘动力学机制研究(JCYB-20080601-4)”与“地球物理场和化学场动态变化与强震活动关系研究(JCYB-20080601-5)”联合资助.

摘要

全文

图/表

参考文献

通过研究2007年6月3日宁洱M_S6.4地震余震序列的三分向记录,为探索横波分裂现象以及上地壳存在裂隙各向异性提供依据,并发现快速S波偏振有两个优势方向,分别为NW140°和NW150°,这与宁洱地区的主应力场方向基本一致。横波分裂延迟时间能够动态反映地下应力场的变化趋势,且较大余震发生之前延迟时间出现大幅度上升。

In this paper,the result of the study about the aftershock-swarm of the M_S6.4 earthquake occurred on June 3,2007 in Ning'er,Yunnan Province was given and the existence of both shear-wave splitting and the extensive dilatancy anisotropy in the upper crust of Ning'er region were recognized.The fast shear wave has two preponderant polarization-directions—NW140°and NW150°,which agree with the regional principal compressive stress.The delay time of the shear wave dynamically responds to the variation of stress field and increases before strong aftershocks.

引言
1 资料选取
2 横波分裂方法
3 结果分析
4 讨论和结论

图1 宁洱6.4级地震序列及流动观测台分布<br/>Fig.1 Distribution of the MS 6.4 Ning'er earthquake and the aftershocks and six temporary stations

图1 宁洱6.4级地震序列及流动观测台分布
Fig.1 Distribution of the MS 6.4 Ning'er earthquake and the aftershocks and six temporary stations

图2 1970年以来宁洱M≥5.0地震震源机制解<br/>Fig.2 Focal mechanism solution of the M≥5.0 earthquakes in Ning'er since 1970

图2 1970年以来宁洱M≥5.0地震震源机制解
Fig.2 Focal mechanism solution of the M≥5.0 earthquakes in Ning'er since 1970

图3 2007年6月25日2时56分宁洱ML1.6地震德化台原始记录和质点运动图<br/>(a)原始记录图;(b)P波质点运动图,左、右框分别<br/>代表南北向和东西向的P波质点运动;(c)水平面<br/>的S波质点运动图,每方框为0.1 s<br/>Fig.3 Original seismogram and particle movement maps at Dehua station on June 25,2007 (a)Original records;(b)P-wave particle motion: the left pane corresponds to the particle motion of SN component, the right pane corresponds to the one of EW component;(c)S-wave particle motion, each plot stands for 0.1s

图3 2007年6月25日2时56分宁洱ML1.6地震德化台原始记录和质点运动图
(a)原始记录图;(b)P波质点运动图,左、右框分别
代表南北向和东西向的P波质点运动;(c)水平面
的S波质点运动图,每方框为0.1 s
Fig.3 Original seismogram and particle movement maps at Dehua station on June 25,2007 (a)Original records;(b)P-wave particle motion: the left pane corresponds to the particle motion of SN component, the right pane corresponds to the one of EW component;(c)S-wave particle motion, each plot stands for 0.1s

图4 2007年6月25日2时56分宁洱ML1.6地震S波分裂图形<br/>(a)快波(S1)、慢波(S2);(b)质点运动图(1、2框时间相连); <br/>TS-P=3.09 s; 快波方位角φ=135°; 延迟时间Δt=0.06 s<br/>Fig.4 Shear wave spliting,of the Ning'er ML 1.6 earthquake on June 25,2007(a)S1 stands for fast-wave, S2 stands for slow-wave;(b)Particle

图4 2007年6月25日2时56分宁洱ML1.6地震S波分裂图形
(a)快波(S1)、慢波(S2);(b)质点运动图(1、2框时间相连);
TS-P=3.09 s; 快波方位角φ=135°; 延迟时间Δt=0.06 s
Fig.4 Shear wave spliting,of the Ning'er ML 1.6 earthquake on June 25,2007(a)S1 stands for fast-wave, S2 stands for slow-wave;(b)Particle

图5 快波偏振方向玫瑰图(a)同心台;(b)宁洱台;(c)德化台;(d)小黑江台<br/>Fig.5 Rose diagrams of the polarization direction of fast shear wave (a)Tongxin station;(b)Ning'er station;(c)Dehua station;(d)Xiaoheijiang station

图5 快波偏振方向玫瑰图(a)同心台;(b)宁洱台;(c)德化台;(d)小黑江台
Fig.5 Rose diagrams of the polarization direction of fast shear wave (a)Tongxin station;(b)Ning'er station;(c)Dehua station;(d)Xiaoheijiang station

图6 同心台(a)和宁洱台(b)慢波延迟时间、震级随时间变化曲线<br/>Fig.6 Change of time delay and earthquake sequence with time (a)Tongxin station;(b)Ning'er station

图6 同心台(a)和宁洱台(b)慢波延迟时间、震级随时间变化曲线
Fig.6 Change of time delay and earthquake sequence with time (a)Tongxin station;(b)Ning'er station

陈慧,叶建庆,刘学军,等.2007.2007年宁洱6.4级地震监测与研究[J].地震研究,30(4):344-349.
高原.2000.破裂临界状态下大理岩的剪切波分裂特征[J].中国地震,16(3):197-202.
李克昌,赵维城,侯学英,等.1980.从思茅、普洱地震探讨断块内部地震地质特征[J].地震研究,3(1):01-05.
李白基.1996.云南禄劝地震余震分裂S波的变化[J].地震学报,18(2):224-230.
李白基,秦嘉政,钱晓东,等.2002.1995年武定6.5级地震余震的S波分裂[J].地震研究,25(2):108～114.
罗省贤,李录明.2003.基于横波分裂的地层裂缝预测方法与应用[J].成都理工大学学报(自然科学版),30(1):52-59.
Crampin S,Atkinson B k.1985.Microcracks in the Earth's crust.First Break,3(3):16-20.
Crampin S,Zatsepin S V.1997.Modelling the compliance of crustal rock-II.Response to temporal changes before earthquakes[J]. Geophys. J. Int, 129:495-506.
Crampin S,Volti T,Stefansson R.1999.A successfully stress-forecast earthquake[J].Geopys.J.Int,138:F1-F5.
Garbin H D,Knopoff L.1973.The compressional modulus of a material by a random distribution of circular cracks[J].Q.Appl.Math,30:453-463.
Garbin H D,Knopoff L.1975a.The shear modulus of a material permeated by a random distribution of circular cracks[J].Q.Appl.Math,33:296-300.
Garbin H D,Knopoff L.1975b.Elastic modulus of a medium with liquid-filled cracks[J].Q.Appl.Math,33:301-303.
Hudson J A.1981.Wave speeds and attenuation of elastic waves in material containing cracks[J].Geophys.J.R.astr.Soc,64:133-150.
Zatsepin S V,Crampin S.1997.Modeling the compliance of crustal rock:I-Response of shear-wave splitting to differential stress[J]. Geophys.J.Int,129:477-494.