2013年芦山M_s7.0地震震源区横波分裂的变化特征
摘要
对2013年芦山Ms7.0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,从位于龙门山断裂带南段芦山地震震源区地震台站的记录中提取了S波分裂的快波偏振方向和慢波的到时延迟.在研究区,观测到各台站的快波偏振优势方向从南向北有分区特征,慢波到时延迟的随时间有趋势性变化.空间上,快波偏振优势方向在南部为北东向,与龙门山断裂走向一致,而北部为北西向,与区域主压应力方向一致,位于断裂带上的台站TQU和BAX表现出特殊性,可能受到龙门山断裂带的直接影响,体现了断裂带上的应力场方向变化的特殊性.时间上,慢波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,芦山地震震源区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.
引文
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邓起东,陈社发,赵小麟.1994.龙门山及其邻区的构造和地震活动及动力学.地震地质,16:389–403
丁志峰,武岩,王辉,等.2008.2008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,38:1600–1604
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高原,刘希强,梁维,等.2004.剪切波分裂系统分析方法(SAM)软件系统.中国地震,20:101–107
石玉涛,高原,赵翠萍,等.2009.汶川地震余震序列的地震介质各向异性.地球物理学报,52:398–407
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Crampin S,Atkinson B K.1985.Microcracks in the Earth’s crust.First Break,3:16–20
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Liu Y,Crampin S,Main I.1997.Shear-wave anisotropy:Spatial and temporal variations in time delays at Parkfield,Central California.Geophys J Int,130:771–785
Mainprice D,Nicolas A.1989.Development of a lattice preferred orientation of minerals.Comput Geosci,16:385–393
Peacock S,Crampin S,Booth D C,et al.1988.Shear-wave splitting in the Anza seismic gap,Southern California:Temporal variations as possible precursors.J Geophys Res,93:3339–3356
Shih X R,Meyer R P,Schneider J F.1989.An automated,analytical method to determine shear-wave splitting.Tectonophysics,165:271–278
Volti T,Crampin S.2003.A four-year study of shear-wave splitting in Iceland:1.Background and preliminary analysis,in New insights into structural interpretation and modeling.J Geol Soc Lond Spec Publ,212:117–133
Wang C Y,Han W B,Wu J P,et al.2007.Crustal structure beneath the eastern margin of the Tibetan Plateau and its tectonic implications.J Geophys Res,112:B07307,doi:10.1029/2005JB003873
Wang Q,Zhang P Z,Freymueller J T,et al.2001.Present-day crustal deformation in China constrained by global positioning system measurements.Science,294:574–577
Zhang Z J,Teng J W,Badal J,et al.2009.Construction of regional and local seismic anisotropic structures from wide-angle seismic data:Crustal deformation in the southeast of China.J Seismol,13:241–252
邓起东,陈社发,赵小麟.1994.龙门山及其邻区的构造和地震活动及动力学.地震地质,16:389–403
丁志峰,武岩,王辉,等.2008.2008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,38:1600–1604
房立华,吴建平,王未来,等.2013.四川芦山Ms7.0级地震及其余震序列重定位.科学通报,58:1901–1909
高原,刘希强,梁维,等.2004.剪切波分裂系统分析方法(SAM)软件系统.中国地震,20:101–107
石玉涛,高原,赵翠萍,等.2009.汶川地震余震序列的地震介质各向异性.地球物理学报,52:398–407
王卫民,郝金来,姚振兴.2013.2013年4月20日四川芦山地震震源破裂过程反演初步结果.地球物理学报,56:1412–1417
吴晶,高原,陈运泰,等.2007.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,50:209–220
谢祖军,金笔凯,郑勇,等.2013.近远震波形反演2013年芦山地震震源参数.中国科学:地球科学,43:1010–1019
姚陈,王培德,陈运泰.1992.卢龙地区S波偏振与上地壳裂隙各向异性.地球物理学报,35:305–315
曾祥方,罗艳,韩立波,等.2013.2013年4月20日四川芦山Ms7.0地震:一个高角度逆冲地震.地球物理学报,56:1418–1424
张培震,徐锡伟,闻学泽,等.2008.2008年汶川8.0级地震发震断裂的滑动速率、复发周期和构造成因.地球物理学报,51:1066–1073
张勇,许力生,陈运泰.2013.芦山4·20地震破裂过程及其致灾特征初步分析.地球物理学报,56:1408–1411
赵珠,范军,郑斯华,等.1997.龙门山断裂带地壳速度结构和震源位置的精确修定.地震学报,19:615–622
郑秀芬,欧阳飚,张东宁,等.2009.“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,52 :1412–1417
Brocher T,Christensen N.1990.Seismic anisotropy due to preferred mineral orientation observed in shallow crustal rocks in southern Alaska.Geology,18:737–740
Chen T C,Booth D C,Crampin S.1987.Shear-wave polarizations near the North Anatolian fault—III.Observations of temporal changes.Geophys J Int,91:287–311
Crampin S,Atkinson B K.1985.Microcracks in the Earth’s crust.First Break,3:16–20
Crampin S,Volti T,Stefansson R.1999.A successfully stress-forecast earthquake.Geophys J Int,138:1–5
Crampin S,Zatsepin S V.1997.Modelling the compliance of crustal rock—II.Response to temporal changes before earthquakes.Geophys J Int,129 :495–506
Gao Y,Crampin S.2004.Observations of stress relaxation before earthquakes.Geophys J Int,157:578–582
Gao Y,Crampin S.2003.Temporal variations of shear-wave splitting in field and laboratory in China.J Appl Geophys,54:279–287
Li Z W,Tian B F,Liu S,et al.2013.Asperity of the 2013 Lushan earthquake in the eastern margin of Tibetan plateau from seismic tomography and aftershock relocation.Geophys J Int,195:2016–2022
Liu Y,Crampin S,Main I.1997.Shear-wave anisotropy:Spatial and temporal variations in time delays at Parkfield,Central California.Geophys J Int,130:771–785
Mainprice D,Nicolas A.1989.Development of a lattice preferred orientation of minerals.Comput Geosci,16:385–393
Peacock S,Crampin S,Booth D C,et al.1988.Shear-wave splitting in the Anza seismic gap,Southern California:Temporal variations as possible precursors.J Geophys Res,93:3339–3356
Shih X R,Meyer R P,Schneider J F.1989.An automated,analytical method to determine shear-wave splitting.Tectonophysics,165:271–278
Volti T,Crampin S.2003.A four-year study of shear-wave splitting in Iceland:1.Background and preliminary analysis,in New insights into structural interpretation and modeling.J Geol Soc Lond Spec Publ,212:117–133
Wang C Y,Han W B,Wu J P,et al.2007.Crustal structure beneath the eastern margin of the Tibetan Plateau and its tectonic implications.J Geophys Res,112:B07307,doi:10.1029/2005JB003873
Wang Q,Zhang P Z,Freymueller J T,et al.2001.Present-day crustal deformation in China constrained by global positioning system measurements.Science,294:574–577
Zhang Z J,Teng J W,Badal J,et al.2009.Construction of regional and local seismic anisotropic structures from wide-angle seismic data:Crustal deformation in the southeast of China.J Seismol,13:241–252
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