四川芦山7.0级强震及其余震序列重定位
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摘要
本研究采用双差定位法对2013年4月20日发生在龙门山断裂带上的四川芦山7.0级强震及主震后48小时内504次余震序列进行重新定位,最终得到328个精定位地震事件.结果表明,余震在水平方向上主要沿龙门山断裂带的山前断裂西南段的大川—双石断裂发生,扩展模式以西南向为主(约23km)兼有弱东北向(约12km),并非简单的单侧扩展.在深度方向上,余震主要以铲状结构分布在18～22km之间.通过拟合精定位后的小震空间分布特征,显示本次地震断层面倾角在15～25km深度范围内由主震处约44°逐渐向西南向扩展增大至约73°,可能表明断层往西南破裂过程中走滑分量逐渐增强,与2008年汶川地震引起中央断裂倾角由西南向东北变化相类似.
Using the double-difference relocation algorithm,we relocated the April 20,2013 Lushan,Sichuan earthquake(MS7.0) and its 504 aftershocks within 48 hours since the mainshock,and finally obtained 328 relocated earthquakes.Our results show that most aftershocks occurred along the Dachuan-Shuangshi fault which situates at the southwestern end of the front range fault in the Longmenshan fault zone,and their extension is predominated by the southwestward movement about 23 km but with the weak northeastward movement around 12 km,which is not a simple single-sided extension.In depth direction,the aftershocks take as a shovel-shaped structure at 18~22 km depth.Fitting the spatial distribution of relocated aftershocks,the results show that the dipping angle of the fault plane gradually increases from 44° around the mainshock at depth of 15~25 km up to 73° when the rupture of the fault extends southwestward,possibly suggesting a gradual increase of striking-slipping component during the southwest rupturing process.This may be similar to that in the central fault caused by the 2008 Wenchuan earthquake.
Using the double-difference relocation algorithm,we relocated the April 20,2013 Lushan,Sichuan earthquake(MS7.0) and its 504 aftershocks within 48 hours since the mainshock,and finally obtained 328 relocated earthquakes.Our results show that most aftershocks occurred along the Dachuan-Shuangshi fault which situates at the southwestern end of the front range fault in the Longmenshan fault zone,and their extension is predominated by the southwestward movement about 23 km but with the weak northeastward movement around 12 km,which is not a simple single-sided extension.In depth direction,the aftershocks take as a shovel-shaped structure at 18~22 km depth.Fitting the spatial distribution of relocated aftershocks,the results show that the dipping angle of the fault plane gradually increases from 44° around the mainshock at depth of 15~25 km up to 73° when the rupture of the fault extends southwestward,possibly suggesting a gradual increase of striking-slipping component during the southwest rupturing process.This may be similar to that in the central fault caused by the 2008 Wenchuan earthquake.
引文
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[12]张勇,许力生,陈运泰.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,2013,56(4):1408-1411.Zhang Y,Xu L S,Chen Y T.Rupture process of the Lushan4.20earthquake and preliminary analysis on the disaster-causing mechanism.Chinese J.Geophys.(in Chinese),2013,56(4):1408-1411.
[13]张勇,许力生,陈运泰.2008年汶川大地震震源机制的时空变化.地球物理学报,2009,52(2):379-389.Zhang Y,Xu L S,Chen Y T.Spatio-temporal variation ofthe source mechanism of the 2008great Wenchuan earthquake.Chinese J.Geophys.(in Chinese),2009,52(2):379-389.
[14]万永革,沈正康,刁桂苓等.利用小震分布和区域应力场确定大震断层面参数方法及其在唐山地震序列中的应用.地球物理学报,2008,51(3):569-583.Wan Y G,Shen Z K,Diao G L,et al.An algorithm of faultparameter determination using distribution of smallearthquakes and parameters of regional stress field and itsapplication to Tangshan earthquake sequence.Chinese J.Geophys.(in Chinese),2008,51(3):569-583.
[15]王福昌,万永革,胡顺田.粒子群算法在主震断层面参数估计中的应用.地震研究,2008,31(2):149-154.Wang F C,Wan Y G,Hu S T.Application of particle swarmoptimization to the estimation of mainshock fault planeparameters.Journal of Seismological Research(in Chinese),2008,31(2):149-154.
[16]曾祥方,罗艳,韩立波等.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,2013,56(4):1418-1424.Zeng X F,Luo Y,Han L B,et al.The Lushan Ms7.0earthquake on 20 April 2013:A high-angle thrust event.Chinese J.Geophys.(in Chinese),2013,56(4):1418-1424.
[17]刘杰,易桂喜,张致伟等.2013年4月20日四川芦山M7.0级地震介绍.地球物理学报,2013,56(4):1404-1407.Liu J,Yi G X,Zhang Z W,et al.Introduction to theLushan,Sichuan M7.0earthquake on 20April 2013.ChineseJ.Geophys.(in Chinese),2013,56(4):1404-1407.
[18]徐锡伟,陈桂华,于贵华等.5.12汶川地震地表破裂基本参数的再论证及其构造内涵分析.地球物理学报,2010,53(10):2321-2336.Xu X W,Chen G H,Yu G H,et a1.Reevaluation of surfacerupture parameters of the 5.12Wenchuan earthquake and itstectonic implication for Tibetan uplift.Chinese J.Geophys.(in Chinese),2010,53(10):2321-2336.
[19]Engdahl E,Villasen A,DeShon H,et al.Teleseismicrelocation and assessment of seismicity(1918—2005)in theregion of the 2004 Mw9.0Sumatra-Andaman and 2005 Mw8.6Nias Island Great Earthquakes.Bull.Seismol.Soc.Am.,2007,97:43-61.
[20]Pesicek J,Thurber C,Zhang H,et al.Teleseismic double-difference relocation of earthquakes along the Sumatra-Andaman subduction zone using a 3-D model.J.Geophys.Res.,2010,115:B10303.
[21]雷建设,赵大鹏,苏金蓉等.龙门山断裂带地壳精细结构与汶川地震发震机理.地球物理学报,2009,52(2):339-345.Lei J S,Zhao D P,Su J R,et al.Fine seismic structure underthe Longmenshan fault zone and the mechanism of the largeWenchuan earthquake.Chinese J.Geophys.(in Chinese),2009,52(2):339-345.
[22]Lei J S,Zhao D P.Structure heterogeneities of theLongmenshan fault zone and the mechanism of the 2008Wenchuan earthquake(Ms8.0).Geochemistry GeophysicsGeosystems,2009,10:Q10010.
[23]Lei J S,Zhao D P,Steinberger B,et al.New seismicconstraints on the upper mantle structure of the Hainanplume.Phys.Earth Planet.Int.,2009,173:33-50.
[24]Lei J S,Xie F R,Mishar O P,et al.The 2011Yingjiang,China,earthquake:A volcano-related fluid-driven earthquake?Bull.Seismol.Soc.Am.,2012,102:417-425.
[2]杨晓平,蒋溥,宋方敏等.龙门山断裂带南段错断晚更新世以来地层的证据.地震地质,1999,4:341-345.Yang X P,Jiang P,Song F M,et al.The evidence of thesouth Longmengshan fault zones cutting late Quaternarystratum.Seismol.Geol.(in Chinese),1999,4:341-345.
[3]王卫民,郝金来,姚振兴.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,2013,56(4):1412-1417.Wang W M,Hao J L,Yao Z X.Preliminary result forrupture process of Apr.20,2013,Lushan Earthquake,Sichuan,China.Chinese J.Geophys.(in Chinese),2013,56(4):1412-1417.
[4]张天中,武巴特尔,黄媛等.近台资料对近震相对定位算法的影响.地球物理学报,2007,50(4):1123-1130.Zhang T Z,Wu Bater,Huang Y,et a1.Effect of the datarecorded at nearby stations on earthquake relative location.Chinese J.Geophys.(in Chinese),2007,50(4):1123-1130.
[5]黄嫒,吴建平,张天中等.汶川8.0级大地震及其余震序列重定位研究.中国科学(D辑),2008,38(10):1242-1249.Huang Y,Wu J P,Zhang T Z,et al.Relocation of the 8.0Wenchuan earthquake and its aftershock sequence.Science inChina(Series D)(in Chinese),2008,38(10):1242-1249.
[6]Waldhauser F,Ellsworth W.A double-difference earthquakelocation algorithm:method and application to the NorthernHayward Fault,California.Bull.Seismol.Soc.Am.,2000,90(6):1353-1368.
[7]赵珠,范军,郑斯华等.龙门山推覆构造带地壳速度结构和震源位置的精确修订.地震学报,1997,19(6):615-622.Zhao Z,Fan J,Zheng S H,et a1.Precision determination ofthe crustal structure and hypocentral locations in theLongmenshan thrust nappe belt.Acta Seismologica Sinica(inChinese),1997,19(6):615-622.
[8]陈九辉,刘启元,李顺成等.汶川Ms8.0地震余震序列重新定位及其地震构造研究.地球物理学报,2009,52(2):390-397.Chen J H,Liu Q Y,Li S C,et al.Seismotectonic study byrelocation of the Wenchuan Ms8.0 earthquake sequence.Chinese J.Geophys.(in Chinese),2009,52(2):390-397.
[9]张广伟,雷建设,谢富仁等.华北地区小震精定位及构造意义.地震学报,2011,33(6):699-714.Zhang G W,Lei J S,Xie F R,et al.Precise relocation ofsmall earthquakes occurred in North China and its tectonicimplication.Acta Seismologica Sinica(in Chinese),2011,33(6):699-714.
[10]房立华,吴建平,张天中等.2011年云南盈江Ms5.8地震及其余震序列重定位.地震学报,2011,33(2):262-267.Fang L H,Wu J P,Zhang T Z,et al.Relocation of mainshockand aftershocks of the 2011Yingjiang Ms5.8earthquake inYunnan.Acta Seismologica Sinica(in Chinese),2011,33(2):262-267.
[11]Lei J S,Zhang G W,Xie F R,et al.Relocation of the 10March 2011 Yingjiang,China,earthquake sequence and itstectonic implications.Earthq.Sci.,2012,25:103-110.
[12]张勇,许力生,陈运泰.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,2013,56(4):1408-1411.Zhang Y,Xu L S,Chen Y T.Rupture process of the Lushan4.20earthquake and preliminary analysis on the disaster-causing mechanism.Chinese J.Geophys.(in Chinese),2013,56(4):1408-1411.
[13]张勇,许力生,陈运泰.2008年汶川大地震震源机制的时空变化.地球物理学报,2009,52(2):379-389.Zhang Y,Xu L S,Chen Y T.Spatio-temporal variation ofthe source mechanism of the 2008great Wenchuan earthquake.Chinese J.Geophys.(in Chinese),2009,52(2):379-389.
[14]万永革,沈正康,刁桂苓等.利用小震分布和区域应力场确定大震断层面参数方法及其在唐山地震序列中的应用.地球物理学报,2008,51(3):569-583.Wan Y G,Shen Z K,Diao G L,et al.An algorithm of faultparameter determination using distribution of smallearthquakes and parameters of regional stress field and itsapplication to Tangshan earthquake sequence.Chinese J.Geophys.(in Chinese),2008,51(3):569-583.
[15]王福昌,万永革,胡顺田.粒子群算法在主震断层面参数估计中的应用.地震研究,2008,31(2):149-154.Wang F C,Wan Y G,Hu S T.Application of particle swarmoptimization to the estimation of mainshock fault planeparameters.Journal of Seismological Research(in Chinese),2008,31(2):149-154.
[16]曾祥方,罗艳,韩立波等.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,2013,56(4):1418-1424.Zeng X F,Luo Y,Han L B,et al.The Lushan Ms7.0earthquake on 20 April 2013:A high-angle thrust event.Chinese J.Geophys.(in Chinese),2013,56(4):1418-1424.
[17]刘杰,易桂喜,张致伟等.2013年4月20日四川芦山M7.0级地震介绍.地球物理学报,2013,56(4):1404-1407.Liu J,Yi G X,Zhang Z W,et al.Introduction to theLushan,Sichuan M7.0earthquake on 20April 2013.ChineseJ.Geophys.(in Chinese),2013,56(4):1404-1407.
[18]徐锡伟,陈桂华,于贵华等.5.12汶川地震地表破裂基本参数的再论证及其构造内涵分析.地球物理学报,2010,53(10):2321-2336.Xu X W,Chen G H,Yu G H,et a1.Reevaluation of surfacerupture parameters of the 5.12Wenchuan earthquake and itstectonic implication for Tibetan uplift.Chinese J.Geophys.(in Chinese),2010,53(10):2321-2336.
[19]Engdahl E,Villasen A,DeShon H,et al.Teleseismicrelocation and assessment of seismicity(1918—2005)in theregion of the 2004 Mw9.0Sumatra-Andaman and 2005 Mw8.6Nias Island Great Earthquakes.Bull.Seismol.Soc.Am.,2007,97:43-61.
[20]Pesicek J,Thurber C,Zhang H,et al.Teleseismic double-difference relocation of earthquakes along the Sumatra-Andaman subduction zone using a 3-D model.J.Geophys.Res.,2010,115:B10303.
[21]雷建设,赵大鹏,苏金蓉等.龙门山断裂带地壳精细结构与汶川地震发震机理.地球物理学报,2009,52(2):339-345.Lei J S,Zhao D P,Su J R,et al.Fine seismic structure underthe Longmenshan fault zone and the mechanism of the largeWenchuan earthquake.Chinese J.Geophys.(in Chinese),2009,52(2):339-345.
[22]Lei J S,Zhao D P.Structure heterogeneities of theLongmenshan fault zone and the mechanism of the 2008Wenchuan earthquake(Ms8.0).Geochemistry GeophysicsGeosystems,2009,10:Q10010.
[23]Lei J S,Zhao D P,Steinberger B,et al.New seismicconstraints on the upper mantle structure of the Hainanplume.Phys.Earth Planet.Int.,2009,173:33-50.
[24]Lei J S,Xie F R,Mishar O P,et al.The 2011Yingjiang,China,earthquake:A volcano-related fluid-driven earthquake?Bull.Seismol.Soc.Am.,2012,102:417-425.
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