2010年玉树7.1级地震震源区横波分裂的变化特征
|
摘要
本文对2010年玉树M_s7.1级地震序列的横波分裂的时空变化现象进行了研究.通过在横波窗内S波质点运动图的分析,从位于甘孜—玉树断裂带台站的地震记录中提取了S波分裂的快波偏振方向和快慢波之间的时间延迟.断裂带上3个台站的S波分裂的结果显示了NEE向快波偏振方向,与区域内最大主压应力方向基本一致.观测到了快、慢波到时延迟的趋势性变化,空间上,位于震源区甘孜—玉树断裂带的北支断裂上L6304和YUS台的到时延迟大于位于南支断裂上的L6303的结果,同时YUS台的到时延迟又大于L6304台的;时间上,YUS台的到时延迟在主震后迅速增大,持续一段时间后又减小.横波分裂现象主要由台站下方岩层中随应力分布排列的微裂隙控制,本文结果揭示了主震和余震过程中区域应力场的变化,玉树地震主震区的应力在主震后得到了释放,地壳应力向东南转移,导致了YUS台的到时延迟大于L6304台的;玉树地震的发震断裂是甘孜—玉树断裂的北支断裂,而南支断裂对其影响较小;YUS台附近的地壳应力在主震后得到了增强,随着余震活动导致的应力释放,后期应力减小.
In this paper, variation of shear wave splitting in the 2010 Yushu M_s7. 1 earthquake sequence was studied. By analyzing S-wave particle motion of local events in the shear wave window, the polarization directions of fast shear waves and the delay times between fast and slow shear waves were derived from seismic recordings at 3 stations near the Garze-Yushu fault belt. The shear wave splitting results of 3 stations in the area of the fault belt reveal the NEE polarization directions of fast shear waves, which are consistent with the direction of regional principal compressive stress. Systematic changes of the time delays between two split shear waves were also observed. As for spatial distribution, in the focal region, the delay times at stations L6304 and YUS in the north branch fault of the Garze-Yushu fault belt are greater than that of station L6303 in the south branch fault, meanwhile, the delay time at station YUS is larger than L6304. In the time domain, after the main shock, the delay times at station YUS increased rapidly, and then reduced after a period of time. Seismic shear wave splitting is caused mostly by stress-aligned microcracks in rock below the stations. The results demonstrate the changes of local stress field during the main-shock and the aftershocks. The stress in the main-shock region was released by the main-shock, the crustal stresses transferred to the southeastern part of the zone, and caused the delay time at station YUS is being greater than L6304. The north branch fault of the Garze-Yushu fault belt is the causative fault of the 2010 Yushu M_s 7. 1 earthquake, whereas the south branch fault has little influence. The stress at station YUS increased after the main-shock, and with the stress release caused by the aftershocks, the stress reduced in the late stage.
In this paper, variation of shear wave splitting in the 2010 Yushu M_s7. 1 earthquake sequence was studied. By analyzing S-wave particle motion of local events in the shear wave window, the polarization directions of fast shear waves and the delay times between fast and slow shear waves were derived from seismic recordings at 3 stations near the Garze-Yushu fault belt. The shear wave splitting results of 3 stations in the area of the fault belt reveal the NEE polarization directions of fast shear waves, which are consistent with the direction of regional principal compressive stress. Systematic changes of the time delays between two split shear waves were also observed. As for spatial distribution, in the focal region, the delay times at stations L6304 and YUS in the north branch fault of the Garze-Yushu fault belt are greater than that of station L6303 in the south branch fault, meanwhile, the delay time at station YUS is larger than L6304. In the time domain, after the main shock, the delay times at station YUS increased rapidly, and then reduced after a period of time. Seismic shear wave splitting is caused mostly by stress-aligned microcracks in rock below the stations. The results demonstrate the changes of local stress field during the main-shock and the aftershocks. The stress in the main-shock region was released by the main-shock, the crustal stresses transferred to the southeastern part of the zone, and caused the delay time at station YUS is being greater than L6304. The north branch fault of the Garze-Yushu fault belt is the causative fault of the 2010 Yushu M_s 7. 1 earthquake, whereas the south branch fault has little influence. The stress at station YUS increased after the main-shock, and with the stress release caused by the aftershocks, the stress reduced in the late stage.
引文
[1] Crampin S,Atkinson B K.Microcracks in the earth's crust.First Break,1985,3(3) :16～20
[2] Crampin S,Zatsepin S V.Modelling the compliance of crustal rock-Ⅱ.Response to temporal changes before earthquakes.Geophys.J.Int.,1997,129:495～506
[3] Gao Y,Crampin S.Observations of stress relaxation before earthquakes.Geophys.J.Int.,2004,157(2) :578～582
[4] Zhang Z J,Teng J W,Badal J,et al.Construction of regional and local seismic anisotropic structures from wideangle seismic data:crustal deformation in the southeast of China.Journal of Seismology,2008,DOI 10． 1007/s10950-008-9124-0
[5] 姚陈,王培德,陈运泰.卢龙地区S波偏振与上地壳裂隙各向异性.地球物理学报,1992,35(3) :305～315 Yao C,Wang P D,Chen Y T.Shear wave polarization and upper crustal crack anisotropy in Lulong.Chinese J.Geophys.(in Chinese),1992,35(3) :305～315
[6] 石玉涛,高原,赵翠萍等.汶川地震余震序列的地震介质各向异性.地球物理学报,2009,52(2) :398～407 Shi Y T,Gao Y,Zhao C P,et al.A study of seismic anisotropy of Wenchuan earthquake sequence.Chinese J.Geophys.(in Chinese),2009,52(2) :398～407
[7] 吴晶,高原,陈运泰等.首都圈西北部地壳介质地震各向异性特征初步研究.地球物理学报,2007,50(1) :209～220 Wu J,Gao Y,Chen Y T,et al.Seismic anisotropy in the crust in Northwestern Capital area of China.Chinese J.Geophys.,2007,50(1) :210～221
[8] Crampin S,Volti T,Stefansson R.A successfully stressforecast earthquake.Geophys J Int,1999,138:F1-F5
[9] Gao Y,Crampin S.Temporal variations of shear-wave splitting in field and laboratory in China.J Appl Geophys,2003,54:279～287
[10] 郑秀芬,陈朝辉,张春贺.1999年台湾集集地震余震区-嘉义地区地震的剪切波分裂参数随时间变化的研究.地球物理学报,2008,51(1) :149～157 Zheng X F,Chen C H,Zhang C H.Study on temporal variations of shear-wave splitting in the Chiayi area,aftershock zone of 1999 Chichi earthquake,Taiwan.Chinese J.Geoptys.(in Chinese).2008,51(1) :149～157
[11] 丁志峰,武岩,王辉等.2008年汶川地震震源区横波分裂的变化特征.中国科学D辑:地球科学,2008,38(12) :1600～1604 Ding Z F,Wu Y,Wang H,et al.Variations of shear wave splitting in the 2008 Wenchuan earthquake region.Science in China(Series D-Earth Sciences),2008,51(12) ,1712～1716
[12] 陈立春,王虎,冉永康等.玉树M_S7． 1级地震地表破裂与历史大地震.科学通报,2010,55:1200～1205 Chen L C,Wang H,Ran Y K,et al.The M_S7． 1 Yushu earthquake surface ruptures and historical earthquakes.Chinese Sci Bull,2010,55,1200～1205
[13] 汪一鹏.青藏高原活动构造基本特征.见:马宗晋,王一鹏,张燕平,主编.青藏高原岩石圈现今变动与动力学.北京:地震出版社,2001． 251～262 Wang Y P.Principal features of the active tectonics in Tibetan Plateau.In:Ma Z,Wang Y,Zhang Y,eds.Study on the Recent Deformation and Dynamics of the Lithosphere of Qinghai-Xizang Plateau(in Chinese).Beijing:Seismologiacl Press,2001． 251～262
[14] 郑秀芬,欧阳飚,张东宁等.“国家数字测震台网数据备份中心”技术系统建设及其对汶川大地震研究的数据支撑.地球物理学报,2009,52(5) :1412～1417 Zheng X F,Ouyang B,Zhang D N,et al.Technical system construction of Data Backup Centre for China Seismograph Network and the data support to researches on the Wenchuan earthquake.Chinese J.Geophys.(in Chinese),2009,52(5) : 1412～1417
[15] Menke W,Brandsdottir B,Jakobsdottir S,et al.Seismic anisotropy in the crust at the mid-Atlantic plate boundary in south-west Iceland.Geophs J Int,1994,119:783～790
[16] Crampin S,Peacock S.A review of shear-wave splitting in the compliant crack-critical anisotropic Earth.Wave Motion,2005,41:59～77
[17] Chen T C,Booth D C,Crampin S.Shear-wave polarizations near the North Anatolian fault-Ⅲ.Observations of temporal changes.Geophys J Royal Astron Soc,1987,91:287～311
[18] Liu Y,Crampin S,Main I.Shear-wave anisotropy:spatial and temporal variations in time delays at Parkfield,Central California.Geophys J Int,1997,130:771～785
[19] Peacock S,Crampin S,Booth D C,et al.Shear-wave splitting in the Anza seismic gap,Southern California:temporal variations as possible precursors.J Geophys Res,1988,93:3339～3356
[20] Shih X R,Meyer R P,Schneider J F.An automated,analytical method to determine shear-wave anisotropy.Tectonophysics,1989,165:271～278
[21] 高原,刘希强,梁维等.剪切波分裂系统分析方法(SAM)软件系统.中国地震,2004,20(1) :101～107 Gao Y,Liu X Q,Liang W,et al.Systematic analysis method of shear-wave splitting:SAM software system.Earthqaake Research in China(in Chinese),2004,20(1) :101～107
[22] Volti T,Crampin S.A four-year study of shear-wave splitting in Iceland:1． Background and preliminary analysis.In:Nieuwland D A ed.New Insights Into Structural Interpretation and Modeling.Geol Soc Lond,Spec Publ,2003,212:117～133
[23] 刘超,许力生,陈运泰.20l0年4月14日青海玉树地震快速矩张量解.地震学报,2010,32:366～368 Liu C,Xu L S,Chen Y T.Quick moment tensor solution for 14 April 2010 Yushu,Qinghai,earthquake.Acta Seismologica Sinica(in Chinese),2010,32(3) :366～368
[24] 张勇,许力生,陈运泰.2010年青海玉树地震震源过程.中国科学D辑:地球科学,2010,40(7) :819～821 Zhang Y,Xu L S,Chen Y T.Source process of the 2010 Yushu,Qinghai,earthquake.Science in China(Series Dearth Sciences),2010,40(7) :819～821
[2] Crampin S,Zatsepin S V.Modelling the compliance of crustal rock-Ⅱ.Response to temporal changes before earthquakes.Geophys.J.Int.,1997,129:495～506
[3] Gao Y,Crampin S.Observations of stress relaxation before earthquakes.Geophys.J.Int.,2004,157(2) :578～582
[4] Zhang Z J,Teng J W,Badal J,et al.Construction of regional and local seismic anisotropic structures from wideangle seismic data:crustal deformation in the southeast of China.Journal of Seismology,2008,DOI 10． 1007/s10950-008-9124-0
[5] 姚陈,王培德,陈运泰.卢龙地区S波偏振与上地壳裂隙各向异性.地球物理学报,1992,35(3) :305～315 Yao C,Wang P D,Chen Y T.Shear wave polarization and upper crustal crack anisotropy in Lulong.Chinese J.Geophys.(in Chinese),1992,35(3) :305～315
[6] 石玉涛,高原,赵翠萍等.汶川地震余震序列的地震介质各向异性.地球物理学报,2009,52(2) :398～407 Shi Y T,Gao Y,Zhao C P,et al.A study of seismic anisotropy of Wenchuan earthquake sequence.Chinese J.Geophys.(in Chinese),2009,52(2) :398～407
[7] 吴晶,高原,陈运泰等.首都圈西北部地壳介质地震各向异性特征初步研究.地球物理学报,2007,50(1) :209～220 Wu J,Gao Y,Chen Y T,et al.Seismic anisotropy in the crust in Northwestern Capital area of China.Chinese J.Geophys.,2007,50(1) :210～221
[8] Crampin S,Volti T,Stefansson R.A successfully stressforecast earthquake.Geophys J Int,1999,138:F1-F5
[9] Gao Y,Crampin S.Temporal variations of shear-wave splitting in field and laboratory in China.J Appl Geophys,2003,54:279～287
[10] 郑秀芬,陈朝辉,张春贺.1999年台湾集集地震余震区-嘉义地区地震的剪切波分裂参数随时间变化的研究.地球物理学报,2008,51(1) :149～157 Zheng X F,Chen C H,Zhang C H.Study on temporal variations of shear-wave splitting in the Chiayi area,aftershock zone of 1999 Chichi earthquake,Taiwan.Chinese J.Geoptys.(in Chinese).2008,51(1) :149～157
[11] 丁志峰,武岩,王辉等.2008年汶川地震震源区横波分裂的变化特征.中国科学D辑:地球科学,2008,38(12) :1600～1604 Ding Z F,Wu Y,Wang H,et al.Variations of shear wave splitting in the 2008 Wenchuan earthquake region.Science in China(Series D-Earth Sciences),2008,51(12) ,1712～1716
[12] 陈立春,王虎,冉永康等.玉树M_S7． 1级地震地表破裂与历史大地震.科学通报,2010,55:1200～1205 Chen L C,Wang H,Ran Y K,et al.The M_S7． 1 Yushu earthquake surface ruptures and historical earthquakes.Chinese Sci Bull,2010,55,1200～1205
[13] 汪一鹏.青藏高原活动构造基本特征.见:马宗晋,王一鹏,张燕平,主编.青藏高原岩石圈现今变动与动力学.北京:地震出版社,2001． 251～262 Wang Y P.Principal features of the active tectonics in Tibetan Plateau.In:Ma Z,Wang Y,Zhang Y,eds.Study on the Recent Deformation and Dynamics of the Lithosphere of Qinghai-Xizang Plateau(in Chinese).Beijing:Seismologiacl Press,2001． 251～262
[14] 郑秀芬,欧阳飚,张东宁等.“国家数字测震台网数据备份中心”技术系统建设及其对汶川大地震研究的数据支撑.地球物理学报,2009,52(5) :1412～1417 Zheng X F,Ouyang B,Zhang D N,et al.Technical system construction of Data Backup Centre for China Seismograph Network and the data support to researches on the Wenchuan earthquake.Chinese J.Geophys.(in Chinese),2009,52(5) : 1412～1417
[15] Menke W,Brandsdottir B,Jakobsdottir S,et al.Seismic anisotropy in the crust at the mid-Atlantic plate boundary in south-west Iceland.Geophs J Int,1994,119:783～790
[16] Crampin S,Peacock S.A review of shear-wave splitting in the compliant crack-critical anisotropic Earth.Wave Motion,2005,41:59～77
[17] Chen T C,Booth D C,Crampin S.Shear-wave polarizations near the North Anatolian fault-Ⅲ.Observations of temporal changes.Geophys J Royal Astron Soc,1987,91:287～311
[18] Liu Y,Crampin S,Main I.Shear-wave anisotropy:spatial and temporal variations in time delays at Parkfield,Central California.Geophys J Int,1997,130:771～785
[19] Peacock S,Crampin S,Booth D C,et al.Shear-wave splitting in the Anza seismic gap,Southern California:temporal variations as possible precursors.J Geophys Res,1988,93:3339～3356
[20] Shih X R,Meyer R P,Schneider J F.An automated,analytical method to determine shear-wave anisotropy.Tectonophysics,1989,165:271～278
[21] 高原,刘希强,梁维等.剪切波分裂系统分析方法(SAM)软件系统.中国地震,2004,20(1) :101～107 Gao Y,Liu X Q,Liang W,et al.Systematic analysis method of shear-wave splitting:SAM software system.Earthqaake Research in China(in Chinese),2004,20(1) :101～107
[22] Volti T,Crampin S.A four-year study of shear-wave splitting in Iceland:1． Background and preliminary analysis.In:Nieuwland D A ed.New Insights Into Structural Interpretation and Modeling.Geol Soc Lond,Spec Publ,2003,212:117～133
[23] 刘超,许力生,陈运泰.20l0年4月14日青海玉树地震快速矩张量解.地震学报,2010,32:366～368 Liu C,Xu L S,Chen Y T.Quick moment tensor solution for 14 April 2010 Yushu,Qinghai,earthquake.Acta Seismologica Sinica(in Chinese),2010,32(3) :366～368
[24] 张勇,许力生,陈运泰.2010年青海玉树地震震源过程.中国科学D辑:地球科学,2010,40(7) :819～821 Zhang Y,Xu L S,Chen Y T.Source process of the 2010 Yushu,Qinghai,earthquake.Science in China(Series Dearth Sciences),2010,40(7) :819～821
版权所有：© 2023 中国地质图书馆 中国地质调查局地学文献中心