龙门山断裂带最新地震活动特征及其意义
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摘要
综合最新布设的龙门山断裂带地震空段台阵(LmsSGA)与四川省地震局固定地震台网数据,对龙门山断裂带新近一年(2016年11月21日到2017年10月28日)的23479个地震事件开展双差定位工作,共获取包括汶川地震余震和芦山地震余震在内的6111个重定位地震事件.在此基础上,分别与汶川地震和芦山地震的早期余震空间分布特征进行比较.研究发现在汶川地震发生近十年后,其余震活动依旧活跃.汶川地震现今余震活动主要分布在10~25km的深度区间,震源深度呈现西南段较东北段偏深的特征.此外,汶川近年余震分布相比早期余震偏深,破裂带西南段的余震活动有向深部迁移的趋势.对于芦山地震,其近期余震活动较弱,余震主要分布在10~15km的深度区间,比早期余震的分布区间偏浅.龙门山断裂带最新余震活动分布特征表明,余震活动随着时间的推移有迁移的现象.考虑到距离主震事件已分别有5~10年的流逝时间,余震迁移现象可能由以流体扩散方式为主的准静态应力机制触发.
Combining the newly established Longmenshan Seismic Gap Array(LmsSGA)with the permanent stations from Sichuan Earthquake Administration,we carry out double-difference location for 23479 events from November 21~(st),2016 to October 28~(th),2017 in Longmenshan Fault Zone and obtain 6111 relocated events including Wenchuan aftershocks and Lushan aftershocks.Comparing with the early aftershocks of Wenchuan event,we find that the aftershocks are still active after ~10 years of Wenchuan earthquake.The Wenchuan aftershocks mainly distribute between 10 to 25 km in depth,and the focal depths in the southwestern section are much deeper compared with the depths in the northeastern section.In addition,compared with the early aftershocks of Wenchuan earthquake,the distribution of the latest aftershocks is much deeper.The aftershocks migrate toward the deeper depth in the most recent years.However,the aftershocks of Lushan earthquake are relatively weak.Moreover,the depths are mainly located between 10 to 15 km,which are much shallower than the earlier aftershocks.The distribution of the latest aftershocks in Longmenshan Fault Zone shows that the aftershocks migrate in space with time.Considering that the elapse time has been 5~10 years after the two mainshocks respectively,we suggest that the aftershock migration may be triggered by quasi-static mechanism,such as fluid diffusion.
Combining the newly established Longmenshan Seismic Gap Array(LmsSGA)with the permanent stations from Sichuan Earthquake Administration,we carry out double-difference location for 23479 events from November 21~(st),2016 to October 28~(th),2017 in Longmenshan Fault Zone and obtain 6111 relocated events including Wenchuan aftershocks and Lushan aftershocks.Comparing with the early aftershocks of Wenchuan event,we find that the aftershocks are still active after ~10 years of Wenchuan earthquake.The Wenchuan aftershocks mainly distribute between 10 to 25 km in depth,and the focal depths in the southwestern section are much deeper compared with the depths in the northeastern section.In addition,compared with the early aftershocks of Wenchuan earthquake,the distribution of the latest aftershocks is much deeper.The aftershocks migrate toward the deeper depth in the most recent years.However,the aftershocks of Lushan earthquake are relatively weak.Moreover,the depths are mainly located between 10 to 15 km,which are much shallower than the earlier aftershocks.The distribution of the latest aftershocks in Longmenshan Fault Zone shows that the aftershocks migrate in space with time.Considering that the elapse time has been 5~10 years after the two mainshocks respectively,we suggest that the aftershock migration may be triggered by quasi-static mechanism,such as fluid diffusion.
引文
Bai M K,Chevalier M L,Pan J W,et al.2018.Southeastward increase of the late quaternary slip-rate of the Xianshuihe fault,eastern Tibet.Geodynamic and seismic hazard implications.Earth and Planetary Science Letters,485:19-31.
Chen L C,Ran Y K,Wang H,et al.2013.The Lushan MS7.0earthquake and activity of the southern segment of the Longmenshan fault zone.Chinese Science Bulletin,58(28-29):3475-3482,doi:10.1007/s11434-013-6009-6.
Chen Y T,Yang Z X,Zhang Y,et al.2013.From 2008Wenchuan earthquake to 2013Lushan earthquake.Scientia Sinica Terrae(in Chinese),43(6):1064-1072.
Clark M K,Royden L H.2000.Topographic ooze:Building the eastern margin of Tibet by lower crustal flow.Geology,28(8):703-706.
Du F,Long F,Ruan X,et al.2013.The M7.0Lushan earthquake and the relationship with the M8.0 Wenchuan earthquake in Sichuan,China.Chinese Journal of Geophysics(in Chinese),56(5):1772-1783,doi:10.6038/cjg20130535.
Fang L H,Wu J P,Wang W L,et al.2015.Aftershock observation and analysis of the 2013 MS7.0 Lushan earthquake.Seismological Research Letters,86(4):1135-1142.
Freed A M.2005.Earthquake triggering by static,dynamic,and postseismic stress transfer.Annual Review of Earth and Planetary Sciences,33:335-367,doi:10.1146/annurev.earth.33.092203.122505.
Gao Y,Wang Q,Zhao B,et al.2013.A rupture blank zone in middle south part of Longmenshan Faults:Effect after Lushan MS7.0earthquake of 20April 2013in Sichuan,China.Science China Earth Sciences,57(9):2036-2044,doi:10.1007/s11430-014-4827-2.
Huang Y,Wu J P,Zhang T Z,et al.2008.Relocation of the MS8.0Wenchuan earthquake and its aftershock sequence.Science in China Series D:Earth Sciences,51(12):1703-1711,doi:10.1007/s11430-008-0135-z.
Hubbard J,Shaw J H.2009.Uplift of the Longmen Shan and Tibetan Plateau,and the 2008 Wenchuan(M=7.9)earthquake.Nature,458(7235):194-197,doi:10.1038/nature07837.
Kato A,Obara K.2014.Step-like migration of early aftershocks following the 2007 MW6.7 Noto-Hanto earthquake,Japan.Geophysical Research Letters,41(11):3864-3869.
Lei J S,Zhao D P.2009.Structural heterogeneity of the Longmenshan fault zone and the mechanism of the 2008 Wenchuan earthquake(MS8.0).Geochemistry,Geophysics,Geosystems,10(10):Q10010,doi:10.1029/2009GC002590.
Lei J S,Zhang G W,Xie F R.2014.The 20April 2013Lushan,Sichuan,mainshock,and its aftershock sequence:Tectonic implications.Earthquake Science,27(1):15-25.
Li Y Q,Jia D,Wang M M,et al.2014.Structural geometry of the source region for the 2013 MW6.6Lushan earthquake:Implication for earthquake hazard assessment along the Longmen Shan.Earth and Planetary Science Letters,390:275-286.
Li Z F,Peng Z G.2016.An automatic phase picker for local earthquakes with predetermined locations:Combining a signalto-noise ratio detector with 1Dvelocity model inversion.Seismological Research Letters,87(6):1397-1405.
Liang C T,Huang Y L,Wang C L,et al.2018.Progress in the studies of the seismic gap between the 2008Wenchuan and 2013Lushan earthquakes.Chinese Journal of Geophysics(in Chinese),61(5):1996-2010,doi:10.6038/cjg2018M0254.
Liu M,Luo G,Wang H.2014.The 2013Lushan earthquake in China tests hazard assessments.SeismologicalResearchLetters,85(1):40-43,doi:10.1785/0220130117.
Lu R Q,Xu X W,He D F,et al.2017.Seismotectonics of the 2013Lushan MW6.7earthquake:Inversion tectonics in the eastern margin of the Tibetan Plateau.Geophysical Research Letters,44(16):8236-8243,doi:10.1002/2017GL074296.
Pei S P,Zhang H J,Su J R,et al.2014.Ductile gap between the Wenchuan and Lushan earthquakes revealed from the twodimensional Pg seismic tomography.Scientific Reports,4:6489,doi:10.1038/srep06489.
Peng Z G,Zhao P.2009.Migration of early aftershocks following the 2004Parkfield earthquake.Nature Geoscience,2(12):877-881,doi:10.1038/ngeo697.
Shan B,Xiong X,Zheng Y,et al.2013.Stress changes on major faults caused by 2013 Lushan earthquake and its relationship with 2008Wenchuan earthquake.Science China Earth Sciences,56(7):1169-1176,doi:10.1007/s11430-013-4642-1.
Shi Z M,Wang G C,Wang C Y,et al.2014.Comparison of hydrological responses to the Wenchuan and Lushan earthquakes.Earth and Planetary Science Letters,391:193-200.
Tang C C,Lin C H,Peng Z G.2014.Spatial-temporal evolution of early aftershocks following the 2010 ML6.4Jiashian earthquake in southern Taiwan.Geophysical Journal International,199(3):1772-1783,doi:10.1093/gji/ggu361.
Thompson T B,Plesch A,Shaw J H,et al.2015.Rapid slip-deficit rates at the eastern margin of the Tibetan Plateau prior to the2008 MW7.9 Wenchuan earthquake.Geophysical Research Letters,42(6):1677-1684,doi:10.1002/2014GL062833.
Waldhauser F,Ellsworth W L.2000.A double-difference earthquake location algorithm:Method and application to the northern Hayward fault,California.Bulletin of the Seismological Society of America,90(6):1353-1368.
Wu J,Yao D D,Meng X F,et al.2017.Spatial-temporal evolutions of early aftershocks following the 2013 MW6.6Lushan earthquake in Sichuan,China.Journal of Geophysical Research:Solid Earth,122(4):2873-2889,doi:10.1002/2016JB013706.
Xu X W,Chen G H,Yu G H,et al.2013.Seismogenic structure of Lushan earthquake and its relationship with Wenchuan earthquake.Earth Science Frontiers(in Chinese),20(3):11-20.
Zhang G W,Lei J S.2013.Relocations of Lushan,Sichuan strong earthquake(MS7.0)and its aftershocks.Chinese Journal of Geophysics(in Chinese),56(5):1764-1771,doi:10.6038/cjg20130534.
Zhang Z J,Wang Y H,Chen Y,et al.2009.Crustal structure across Longmenshan fault belt from passive source seismic profiling.Geophysical Research Letters,36(17):L17310,1397-1413,doi:10.1029/2009GL039580.
Zhao B,Shi Y T,Gao Y.2011.Relocation of the Wenchuan MS8.0Earthquake Sequence.Earthquake(in Chinese),31(2):1-10.
Zhao B,Gao Y,Huang Z B,et al.2013.Double difference relocation,focal mechanism and stress inversion of Lushan MS7.0earthquake sequence.Chinese Journal of Geophysics(in Chinese),56(10):3385-3395,doi:10.6038/cjg20131014.
Zhao Z,Zhang R S.1987.Primary study of crustal and upper mantle velocity structure of Sichuan province.Acta Seismologica Sinica(in Chinese),9(2):154-166.
Zheng Y,Ge C,Xie Z J,et al.2013.Crustal and upper mantle structure and the deep seismogenic environment in the source regions of the Lushan earthquake and the Wenchuan earthquake.Science China Earth Sciences,56(7):1158-1168,doi:10.1007/s11430-013-4641-2.
陈立春,冉勇康,王虎等.2013.芦山地震与龙门山断裂带南段活动性.科学通报,58(20):1925-1932.
陈运泰,杨智娴,张勇等.2013.从汶川地震到芦山地震.中国科学:地球科学,43(6):1064-1072.
杜方,龙锋,阮祥等.2013.四川芦山7.0级地震及其与汶川8.0级地震的关系.地球物理学报,56(5):1772-1783,doi:10.6038/cjg20130535.
高原,王琼,赵博等.2013.龙门山断裂带中南段的一个破裂空段---芦山地震的震后效应.中国科学:地球科学,43(6):1038-1046.
黄媛,吴建平,张天中等.2008.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:地球科学,38(10):1242-1249.
梁春涛,黄焱羚,王朝亮等.2018.汶川和芦山地震之间地震空区综合研究进展.地球物理学报,61(5):1996-2010,doi:10.6038/cjg2018M0254.
单斌,熊熊,郑勇等.2013.2013年芦山地震导致的周边断层应力变化及其与2008年汶川地震的关系.中国科学:地球科学,43(6):1002-1009.
徐锡伟,陈桂华,于贵华等.2013.芦山地震发震构造及其与汶川地震关系讨论.地学前缘,20(3):11-20.
张广伟,雷建设.2013.四川芦山7.0级强震及其余震序列重定位.地球物理学报,56(5):1764-1771,doi:10.6038/cjg20130534.
赵博,石玉涛,高原.2011.汶川MS8.0地震及余震序列重新定位.地震,31(2):1-10.
赵博,高原,黄志斌等.2013.四川芦山MS7.0地震余震序列双差定位、震源机制及应力场反演.地球物理学报,56(10):3385-3395,doi:10.6038/cjg20131014.
赵珠,张润生.1987.四川地区地壳上地幔速度结构的初步研究.地震学报,9(2):44-56.
郑勇,葛粲,谢祖军等.2013.芦山与汶川地震震区地壳上地幔结构及深部孕震环境.中国科学:地球科学,43(6):1027-1037.
Chen L C,Ran Y K,Wang H,et al.2013.The Lushan MS7.0earthquake and activity of the southern segment of the Longmenshan fault zone.Chinese Science Bulletin,58(28-29):3475-3482,doi:10.1007/s11434-013-6009-6.
Chen Y T,Yang Z X,Zhang Y,et al.2013.From 2008Wenchuan earthquake to 2013Lushan earthquake.Scientia Sinica Terrae(in Chinese),43(6):1064-1072.
Clark M K,Royden L H.2000.Topographic ooze:Building the eastern margin of Tibet by lower crustal flow.Geology,28(8):703-706.
Du F,Long F,Ruan X,et al.2013.The M7.0Lushan earthquake and the relationship with the M8.0 Wenchuan earthquake in Sichuan,China.Chinese Journal of Geophysics(in Chinese),56(5):1772-1783,doi:10.6038/cjg20130535.
Fang L H,Wu J P,Wang W L,et al.2015.Aftershock observation and analysis of the 2013 MS7.0 Lushan earthquake.Seismological Research Letters,86(4):1135-1142.
Freed A M.2005.Earthquake triggering by static,dynamic,and postseismic stress transfer.Annual Review of Earth and Planetary Sciences,33:335-367,doi:10.1146/annurev.earth.33.092203.122505.
Gao Y,Wang Q,Zhao B,et al.2013.A rupture blank zone in middle south part of Longmenshan Faults:Effect after Lushan MS7.0earthquake of 20April 2013in Sichuan,China.Science China Earth Sciences,57(9):2036-2044,doi:10.1007/s11430-014-4827-2.
Huang Y,Wu J P,Zhang T Z,et al.2008.Relocation of the MS8.0Wenchuan earthquake and its aftershock sequence.Science in China Series D:Earth Sciences,51(12):1703-1711,doi:10.1007/s11430-008-0135-z.
Hubbard J,Shaw J H.2009.Uplift of the Longmen Shan and Tibetan Plateau,and the 2008 Wenchuan(M=7.9)earthquake.Nature,458(7235):194-197,doi:10.1038/nature07837.
Kato A,Obara K.2014.Step-like migration of early aftershocks following the 2007 MW6.7 Noto-Hanto earthquake,Japan.Geophysical Research Letters,41(11):3864-3869.
Lei J S,Zhao D P.2009.Structural heterogeneity of the Longmenshan fault zone and the mechanism of the 2008 Wenchuan earthquake(MS8.0).Geochemistry,Geophysics,Geosystems,10(10):Q10010,doi:10.1029/2009GC002590.
Lei J S,Zhang G W,Xie F R.2014.The 20April 2013Lushan,Sichuan,mainshock,and its aftershock sequence:Tectonic implications.Earthquake Science,27(1):15-25.
Li Y Q,Jia D,Wang M M,et al.2014.Structural geometry of the source region for the 2013 MW6.6Lushan earthquake:Implication for earthquake hazard assessment along the Longmen Shan.Earth and Planetary Science Letters,390:275-286.
Li Z F,Peng Z G.2016.An automatic phase picker for local earthquakes with predetermined locations:Combining a signalto-noise ratio detector with 1Dvelocity model inversion.Seismological Research Letters,87(6):1397-1405.
Liang C T,Huang Y L,Wang C L,et al.2018.Progress in the studies of the seismic gap between the 2008Wenchuan and 2013Lushan earthquakes.Chinese Journal of Geophysics(in Chinese),61(5):1996-2010,doi:10.6038/cjg2018M0254.
Liu M,Luo G,Wang H.2014.The 2013Lushan earthquake in China tests hazard assessments.SeismologicalResearchLetters,85(1):40-43,doi:10.1785/0220130117.
Lu R Q,Xu X W,He D F,et al.2017.Seismotectonics of the 2013Lushan MW6.7earthquake:Inversion tectonics in the eastern margin of the Tibetan Plateau.Geophysical Research Letters,44(16):8236-8243,doi:10.1002/2017GL074296.
Pei S P,Zhang H J,Su J R,et al.2014.Ductile gap between the Wenchuan and Lushan earthquakes revealed from the twodimensional Pg seismic tomography.Scientific Reports,4:6489,doi:10.1038/srep06489.
Peng Z G,Zhao P.2009.Migration of early aftershocks following the 2004Parkfield earthquake.Nature Geoscience,2(12):877-881,doi:10.1038/ngeo697.
Shan B,Xiong X,Zheng Y,et al.2013.Stress changes on major faults caused by 2013 Lushan earthquake and its relationship with 2008Wenchuan earthquake.Science China Earth Sciences,56(7):1169-1176,doi:10.1007/s11430-013-4642-1.
Shi Z M,Wang G C,Wang C Y,et al.2014.Comparison of hydrological responses to the Wenchuan and Lushan earthquakes.Earth and Planetary Science Letters,391:193-200.
Tang C C,Lin C H,Peng Z G.2014.Spatial-temporal evolution of early aftershocks following the 2010 ML6.4Jiashian earthquake in southern Taiwan.Geophysical Journal International,199(3):1772-1783,doi:10.1093/gji/ggu361.
Thompson T B,Plesch A,Shaw J H,et al.2015.Rapid slip-deficit rates at the eastern margin of the Tibetan Plateau prior to the2008 MW7.9 Wenchuan earthquake.Geophysical Research Letters,42(6):1677-1684,doi:10.1002/2014GL062833.
Waldhauser F,Ellsworth W L.2000.A double-difference earthquake location algorithm:Method and application to the northern Hayward fault,California.Bulletin of the Seismological Society of America,90(6):1353-1368.
Wu J,Yao D D,Meng X F,et al.2017.Spatial-temporal evolutions of early aftershocks following the 2013 MW6.6Lushan earthquake in Sichuan,China.Journal of Geophysical Research:Solid Earth,122(4):2873-2889,doi:10.1002/2016JB013706.
Xu X W,Chen G H,Yu G H,et al.2013.Seismogenic structure of Lushan earthquake and its relationship with Wenchuan earthquake.Earth Science Frontiers(in Chinese),20(3):11-20.
Zhang G W,Lei J S.2013.Relocations of Lushan,Sichuan strong earthquake(MS7.0)and its aftershocks.Chinese Journal of Geophysics(in Chinese),56(5):1764-1771,doi:10.6038/cjg20130534.
Zhang Z J,Wang Y H,Chen Y,et al.2009.Crustal structure across Longmenshan fault belt from passive source seismic profiling.Geophysical Research Letters,36(17):L17310,1397-1413,doi:10.1029/2009GL039580.
Zhao B,Shi Y T,Gao Y.2011.Relocation of the Wenchuan MS8.0Earthquake Sequence.Earthquake(in Chinese),31(2):1-10.
Zhao B,Gao Y,Huang Z B,et al.2013.Double difference relocation,focal mechanism and stress inversion of Lushan MS7.0earthquake sequence.Chinese Journal of Geophysics(in Chinese),56(10):3385-3395,doi:10.6038/cjg20131014.
Zhao Z,Zhang R S.1987.Primary study of crustal and upper mantle velocity structure of Sichuan province.Acta Seismologica Sinica(in Chinese),9(2):154-166.
Zheng Y,Ge C,Xie Z J,et al.2013.Crustal and upper mantle structure and the deep seismogenic environment in the source regions of the Lushan earthquake and the Wenchuan earthquake.Science China Earth Sciences,56(7):1158-1168,doi:10.1007/s11430-013-4641-2.
陈立春,冉勇康,王虎等.2013.芦山地震与龙门山断裂带南段活动性.科学通报,58(20):1925-1932.
陈运泰,杨智娴,张勇等.2013.从汶川地震到芦山地震.中国科学:地球科学,43(6):1064-1072.
杜方,龙锋,阮祥等.2013.四川芦山7.0级地震及其与汶川8.0级地震的关系.地球物理学报,56(5):1772-1783,doi:10.6038/cjg20130535.
高原,王琼,赵博等.2013.龙门山断裂带中南段的一个破裂空段---芦山地震的震后效应.中国科学:地球科学,43(6):1038-1046.
黄媛,吴建平,张天中等.2008.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:地球科学,38(10):1242-1249.
梁春涛,黄焱羚,王朝亮等.2018.汶川和芦山地震之间地震空区综合研究进展.地球物理学报,61(5):1996-2010,doi:10.6038/cjg2018M0254.
单斌,熊熊,郑勇等.2013.2013年芦山地震导致的周边断层应力变化及其与2008年汶川地震的关系.中国科学:地球科学,43(6):1002-1009.
徐锡伟,陈桂华,于贵华等.2013.芦山地震发震构造及其与汶川地震关系讨论.地学前缘,20(3):11-20.
张广伟,雷建设.2013.四川芦山7.0级强震及其余震序列重定位.地球物理学报,56(5):1764-1771,doi:10.6038/cjg20130534.
赵博,石玉涛,高原.2011.汶川MS8.0地震及余震序列重新定位.地震,31(2):1-10.
赵博,高原,黄志斌等.2013.四川芦山MS7.0地震余震序列双差定位、震源机制及应力场反演.地球物理学报,56(10):3385-3395,doi:10.6038/cjg20131014.
赵珠,张润生.1987.四川地区地壳上地幔速度结构的初步研究.地震学报,9(2):44-56.
郑勇,葛粲,谢祖军等.2013.芦山与汶川地震震区地壳上地幔结构及深部孕震环境.中国科学:地球科学,43(6):1027-1037.