2017年西藏米林M_S6.9地震余震序列重定位和b值时空分布特征
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摘要
本文采用双差定位方法对2017年西藏米林M_S6.9地震的余震序列进行重定位,获得了较准确的余震空间分布。在此基础上,计算了米林地震震源区的b值空间分布,并结合前人资料研究了米林地震前后的b值变化。重定位结果显示:米林地震余震序列呈NW-SE向分布,主要分布在雅鲁藏布江大拐弯缝合带和比鲁构造岩片的北东边界,震源深度集中于3—20 km范围内。b值时间分布显示:米林地震震前震源区的b值降低,表明震前震源区存在较强的应力积累;地震后震源区的b值呈现跳跃式上升,反映出震源区应力释放,同时随时间的推移,b值逐渐趋于稳定。米林地震震源区的b值在0.52—1.35范围内变化,15 km深度以上b值在东、西方向上存在差异,15 km以下在东北、南西方向上存在差异,由此推测不同的b值分布与地下的结构特征有关,浅层的b值变化与震源区的破裂程度相关,深部变化则反映了不同构造单元的岩性差异。
The aftershock sequence of the Milin MS6.9 earthquake in Tibet in 2017 are relocated by double-difference algorithm in this paper. Based on the relocated results,the spatial distribution of b-value in the source region of Milin earthquake is obtained. Combining historical b-value data from previous researches,the temporal distribution of b-value in the studied area is also obtained. The relocation results show that the aftershock sequence of the Milin earthquake are distributed in NE-SE direction along the NE boundary of Indus-Yarlung Tsangpo big-turned suture and Bilu tectonic slice,most aftershocks are concentrated in 3-20 km depth. The temporal distribution of b-value shows before Milin earthquake b-value is lower than that in the year of 2008,indicating that the stress accumulation in the studied area is strong before Milin earthquake. After Milin earthquake,there was a step-rise of b-value,showing the releases of stress,and b-value tended to stable. b-value ranges in 0.52-1.35 in the source region of Milin earthquake,the b-value variation above the depth of 15 km is distributed along the east-west direction,and below 15 km along the NE-SW direction. Therefore,it is deduced that different bvalue distribution represents different structure characteristics,i.e.,the b-value variation of the shallow area is related to the degree of rupture in the source region,and the b-value variation of deep area reflects the lithology difference of different tectonic units.
The aftershock sequence of the Milin MS6.9 earthquake in Tibet in 2017 are relocated by double-difference algorithm in this paper. Based on the relocated results,the spatial distribution of b-value in the source region of Milin earthquake is obtained. Combining historical b-value data from previous researches,the temporal distribution of b-value in the studied area is also obtained. The relocation results show that the aftershock sequence of the Milin earthquake are distributed in NE-SE direction along the NE boundary of Indus-Yarlung Tsangpo big-turned suture and Bilu tectonic slice,most aftershocks are concentrated in 3-20 km depth. The temporal distribution of b-value shows before Milin earthquake b-value is lower than that in the year of 2008,indicating that the stress accumulation in the studied area is strong before Milin earthquake. After Milin earthquake,there was a step-rise of b-value,showing the releases of stress,and b-value tended to stable. b-value ranges in 0.52-1.35 in the source region of Milin earthquake,the b-value variation above the depth of 15 km is distributed along the east-west direction,and below 15 km along the NE-SW direction. Therefore,it is deduced that different bvalue distribution represents different structure characteristics,i.e.,the b-value variation of the shallow area is related to the degree of rupture in the source region,and the b-value variation of deep area reflects the lithology difference of different tectonic units.
引文
白玲,李国辉,宋博文. 2017. 2017年西藏米林6.9级地震震源参数及其构造意义[J].地球物理学报,60(12):4956–4963.Bai L,Li G H,Song B W. 2017. The source parameters of the M6.9 Mainling,Tibet earthquake and its tectonic implications[J].Chinese Journal of Geophysics,60(12):4956–4963(in Chinese).
程成,白玲,丁林,李国辉,杨建亚,许强. 2017.利用接收函数方法研究喜马拉雅东构造结地区地壳结构[J].地球物理学报,60(8):2969–2979.Cheng C,Bai L,Ding L,Li G H,Yang J Y,Xu Q. 2017. Crustal structure of Eastern Himalayan Syntaxis revealed by receiver function method[J]. Chinese Journal of Geophysics,60(8):2969–2979(in Chinese).
方亚如,蔡戴恩,刘晓红,李纪汉,郝晋昇,耿乃光. 1986.含水岩石破裂前的声发射b值变化[J].地震,(2):1–6.Fang Y R,Cai D E,Liu X H,Li J H,Hao J S,Geng N G. 1986. The change of b-value of acoustic emission before ruptures of water-bearing rocks[J]. Earthquake,(2):1–6(in Chinese).
黄亦磊,周仕勇,庄建仓. 2016.基于地震目录估计完备震级方法的数值实验[J].地球物理学报,59(4):1350–1358.Huang Y L,Zhou S Y,Zhuang J C. 2016. Numerical tests on catalog-based methods to estimate magnitude of completeness[J].Chinese Journal of Geophysics,59(4):1350–1358(in Chinese).
李莹甄,殷娜,李小晗. 2014.不同震级标度转换关系研究概述[J].地震工程学报,36(1):80–87.Li Y Z,Yin N,Li X H. 2014. Review of the conversional relationship for different magnitude scales[J]. China Earthquake Engineering Journal,36(1):80–87(in Chinese).
邵翠茹. 2009.雅鲁藏布大峡谷地区地震活动性研究[D].北京:中国地震局地球物理研究所:51–68.Shao C R. 2009. Seismicity of the Yarlung Tsangpo Grand Canyon Region,China[D]. Beijing:Institute of Geophysics,China Earthquake Administration:51–68(in Chinese).
王鹏,侯金欣,吴朋. 2017. 2017年九寨沟MS7.0地震序列活动特征分析[J].中国地震,33(4):453–462.Wang P,Hou J X,Wu P. 2017. Temporal evolution of the seismicity of the 2017 Jiuzhaigou MS7.0 earthquake sequence[J].Earthquake Research in China,33(4):453–462(in Chinese).
王未来,吴建平,房立华,王长在. 2012. 2010年玉树MS7.1地震及其余震的双差定位研究[J].中国科学:地球科学,42 (7):1037–1046.Wang W L,Wu J P,Fang L H,Wang C Z. 2013. Relocation of the Yushu MS7.1 earthquake and its aftershocks in 2010 from HypoDD[J]. Science China Earth Sciences,56(2):182–191.
王未来,吴建平,房立华,来贵娟. 2014. 2014年云南鲁甸MS6.5地震序列的双差定位[J].地球物理学报,57(9):3042–3051.Wang W L,Wu J P,Fang L H,Lai G J. 2014. Double difference location of the Ludian MS6.5 earthquake sequences in Yunnan Province in 2014[J]. Chinese Journal of Geophysics,57(9):3042–3051(in Chinese).
张盛峰,吴忠良,房立华. 2014.双差(DD)定位地震目录能用于地震序列的统计地震学参数计算吗?:云南鲁甸MS6.5地震序列b值的空间分布[J].地震地质,36(4):1244–1259.Zhang S F,Wu Z L,Fang L H. 2014. Can the DD-relocated earthquake catalogue be used for the statistical parameters of an earthquake sequence?:A case study of the spatial distribution of b-values for the aftershocks of the 2014 Ludian MS6.5 earthquake[J]. Seismology and Geology,36(4):1244–1259(in Chinese).
张勇,许力生,陈运泰. 2017. 2017年11月18日西藏米林6.9级地震(应急处置科技产品报告)[EB/OL].[2018-04-20].http://www.cea-igp.ac.cn/tpxw/276003.html.Zhang Y, Xu L, Chen Y T. 2017. Earthquake summary poster for November 18, 2017, Milin, Tibet, MS6.9 earthquake[EB/OL].[2018-04-20]. http://www.cea-igp.ac.cn/tpxw/276003.html(in Chinese).
郑钰,杨建思. 2008.双差算法的剖析及参数对定位的影响[J].地震地磁观测与研究,29(3):85–93.Zheng Y,Yang J S. 2008. Analysis of double-difference algorithm and the affect of its parameter in location[J]. Seismological and Geomagnetic Observation and Research,29(3):85–93(in Chinese).
Aki K. 1965. Maximum likelihood estimate of b in the formula log N=a-bM and its confidence limits[J]. Bull Seismol Soc Am,43 :237–239.
Amitrano D. 2003. Brittle-ductile transition and associated seismicity:Experimental and numerical studies and relationship with the b value[J]. J Geophys Res,108(B1):ESE 19-1–ESE 19-15.
Dziewonski A M,Chou T A,Woodhouse J H. 1981. Determination of earthquake source parameters from waveform data for studies of global and regional seismicity[J]. J Geophys Res,86:2825–2852.
Ekstr?m G,Nettles M,Dziewonski A M. 2012. The global CMT project 2004-2010:Centroid-moment tensors for 13 017 earthquakes[J]. Phys Earth Planet Inter,200:1–9.
Frohlich C,Davis S D. 1993. Teleseismic b values;Or,much ado about 1.0[J]. J Geophys Res,98(B1):631–644.
Gupta H K. 2002. A review of recent studies of triggered earthquakes by artificial water reservoirs with special emphasis on earthquakes in Koyna,India[J]. Earth-Sci Rev,58(3/4):279–310.
Gutenberg B,Richter C F. 1954. Seismicity of the Earth and Associated Phenomena[M]. 2nd ed. Princeton:Princeton University Press:1–310.
Mogi K. 1962. Study of elastic shocks caused by the fracture of heterogeneous materials and its relations to earthquake phenomena[J].Bull Earthq Res Inst,Univ Tokyo,40(1):125–173.
Mogi K. 1967. Regional variations in magnitude-frequency relation of earthquakes[J]. Bull Earthq Res Inst,Univ Tokyo,45(2):313 –325.
Nakaya S. 2006. Spatio-temporal variation in b value within the subducting slab prior to the 2003 Tokachi-Oki earthquake(M8.0),Japan[J]. J Geophys Res,111(B3):B03311.
Nuannin P,Kulhánek O,Persson L. 2012. Variations of b-values preceding large earthquakes in the Andaman-Sumatra subduction zone[J]. J Asian Earth Sci,61:237–242.
Papazachos B C. 1974. Dependence of the seismic parameter b on the magnitude range[J]. Pure Appl Geophys,112(6):1059–1065.
Rydelek P A,Sacks I S. 1989. Testing the completeness of earthquake catalogues and the hypothesis of self-similarity[J].Nature,337(6204):251–253.
Scholz C H. 1968. The frequency-magnitude relation of microfracturing in rock and its relation to earthquakes[J]. Bull Seismol Soc Am,58(9):399–415.
Schorlemmer D,Wiemer S,Wyss M,Jackson D D. 2004. Earthquake statistics at Parkfield:2. Probabilistic forecasting and testing[J]. J Geophys Res,109(B12):B12308.
Schorlemmer D,Wiemer S,Wyss M. 2005. Variations in earthquake-size distribution across different stress regimes[J]. Nature,434 (7058):539–542.
Shi Y L,Bolt B A. 1982. The standard error of the magnitude-frequency b value[J]. Bull Seismol Soc Am,72(5):1677–1687.
Smith W D. 1981. The b-value as an earthquake precursor[J]. Nature,289(5794):136–139.
Waldhauser F,Ellsworth W L. 2000. A double-difference earthquake location algorithm:Method and application to the northern Hayward fault,California[J]. Bull Seismol Soc Am,90(6):1353–1368.
Waldhauser F,Ellsworth W L. 2002. Fault structure and mechanics of the Hayward fault,California,from double-difference earthquake locations[J]. J Geophys Res,107(B3):ESE 3-1–ESE 3-15.
Wiemer S,Katsumata K. 1999. Spatial variability of seismicity parameters in aftershock zones[J]. J Geophys Res,104(B6):13135–13151.
Wiemer S,Wyss M. 2000. Minimum magnitude of completeness in earthquake catalogs:Examples from Alaska,the western United States,and Japan[J]. Bull Seismol Soc Am,90(4):859–869.
Wiemer S,Gerstenberge M,Hauksson E. 2002. Properties of the aftershock sequence of the 1999 MW7.1 Hector Mine earthquake:Implications for aftershock hazard[J]. Bull Seismol Soc Am,90(4):1227–1240.
Xu Z Q,Ji S C,Cai Z H,Zeng L S,Geng Q R,Cao H. 2012. Kinematics and dynamics of the Namche Barwa Syntaxis,eastern Himalaya:Constraints from deformation,fabrics and geochronology[J]. Gondwana Res,21(1):19–36.
Zeitler P K,Meltzer A S,Brown L,Kidd W S F,Lim C,Enkelmann E. 2014. Tectonics and topographic evolution of Namche Barwa and the easternmost Lhasa block,Tibet[G]//Toward an Improved Understanding of Uplift Mechanisms and the Elevation History of the Tibetan Plateau. Colorado:Geological Society of America,507:23–58.
程成,白玲,丁林,李国辉,杨建亚,许强. 2017.利用接收函数方法研究喜马拉雅东构造结地区地壳结构[J].地球物理学报,60(8):2969–2979.Cheng C,Bai L,Ding L,Li G H,Yang J Y,Xu Q. 2017. Crustal structure of Eastern Himalayan Syntaxis revealed by receiver function method[J]. Chinese Journal of Geophysics,60(8):2969–2979(in Chinese).
方亚如,蔡戴恩,刘晓红,李纪汉,郝晋昇,耿乃光. 1986.含水岩石破裂前的声发射b值变化[J].地震,(2):1–6.Fang Y R,Cai D E,Liu X H,Li J H,Hao J S,Geng N G. 1986. The change of b-value of acoustic emission before ruptures of water-bearing rocks[J]. Earthquake,(2):1–6(in Chinese).
黄亦磊,周仕勇,庄建仓. 2016.基于地震目录估计完备震级方法的数值实验[J].地球物理学报,59(4):1350–1358.Huang Y L,Zhou S Y,Zhuang J C. 2016. Numerical tests on catalog-based methods to estimate magnitude of completeness[J].Chinese Journal of Geophysics,59(4):1350–1358(in Chinese).
李莹甄,殷娜,李小晗. 2014.不同震级标度转换关系研究概述[J].地震工程学报,36(1):80–87.Li Y Z,Yin N,Li X H. 2014. Review of the conversional relationship for different magnitude scales[J]. China Earthquake Engineering Journal,36(1):80–87(in Chinese).
邵翠茹. 2009.雅鲁藏布大峡谷地区地震活动性研究[D].北京:中国地震局地球物理研究所:51–68.Shao C R. 2009. Seismicity of the Yarlung Tsangpo Grand Canyon Region,China[D]. Beijing:Institute of Geophysics,China Earthquake Administration:51–68(in Chinese).
王鹏,侯金欣,吴朋. 2017. 2017年九寨沟MS7.0地震序列活动特征分析[J].中国地震,33(4):453–462.Wang P,Hou J X,Wu P. 2017. Temporal evolution of the seismicity of the 2017 Jiuzhaigou MS7.0 earthquake sequence[J].Earthquake Research in China,33(4):453–462(in Chinese).
王未来,吴建平,房立华,王长在. 2012. 2010年玉树MS7.1地震及其余震的双差定位研究[J].中国科学:地球科学,42 (7):1037–1046.Wang W L,Wu J P,Fang L H,Wang C Z. 2013. Relocation of the Yushu MS7.1 earthquake and its aftershocks in 2010 from HypoDD[J]. Science China Earth Sciences,56(2):182–191.
王未来,吴建平,房立华,来贵娟. 2014. 2014年云南鲁甸MS6.5地震序列的双差定位[J].地球物理学报,57(9):3042–3051.Wang W L,Wu J P,Fang L H,Lai G J. 2014. Double difference location of the Ludian MS6.5 earthquake sequences in Yunnan Province in 2014[J]. Chinese Journal of Geophysics,57(9):3042–3051(in Chinese).
张盛峰,吴忠良,房立华. 2014.双差(DD)定位地震目录能用于地震序列的统计地震学参数计算吗?:云南鲁甸MS6.5地震序列b值的空间分布[J].地震地质,36(4):1244–1259.Zhang S F,Wu Z L,Fang L H. 2014. Can the DD-relocated earthquake catalogue be used for the statistical parameters of an earthquake sequence?:A case study of the spatial distribution of b-values for the aftershocks of the 2014 Ludian MS6.5 earthquake[J]. Seismology and Geology,36(4):1244–1259(in Chinese).
张勇,许力生,陈运泰. 2017. 2017年11月18日西藏米林6.9级地震(应急处置科技产品报告)[EB/OL].[2018-04-20].http://www.cea-igp.ac.cn/tpxw/276003.html.Zhang Y, Xu L, Chen Y T. 2017. Earthquake summary poster for November 18, 2017, Milin, Tibet, MS6.9 earthquake[EB/OL].[2018-04-20]. http://www.cea-igp.ac.cn/tpxw/276003.html(in Chinese).
郑钰,杨建思. 2008.双差算法的剖析及参数对定位的影响[J].地震地磁观测与研究,29(3):85–93.Zheng Y,Yang J S. 2008. Analysis of double-difference algorithm and the affect of its parameter in location[J]. Seismological and Geomagnetic Observation and Research,29(3):85–93(in Chinese).
Aki K. 1965. Maximum likelihood estimate of b in the formula log N=a-bM and its confidence limits[J]. Bull Seismol Soc Am,43 :237–239.
Amitrano D. 2003. Brittle-ductile transition and associated seismicity:Experimental and numerical studies and relationship with the b value[J]. J Geophys Res,108(B1):ESE 19-1–ESE 19-15.
Dziewonski A M,Chou T A,Woodhouse J H. 1981. Determination of earthquake source parameters from waveform data for studies of global and regional seismicity[J]. J Geophys Res,86:2825–2852.
Ekstr?m G,Nettles M,Dziewonski A M. 2012. The global CMT project 2004-2010:Centroid-moment tensors for 13 017 earthquakes[J]. Phys Earth Planet Inter,200:1–9.
Frohlich C,Davis S D. 1993. Teleseismic b values;Or,much ado about 1.0[J]. J Geophys Res,98(B1):631–644.
Gupta H K. 2002. A review of recent studies of triggered earthquakes by artificial water reservoirs with special emphasis on earthquakes in Koyna,India[J]. Earth-Sci Rev,58(3/4):279–310.
Gutenberg B,Richter C F. 1954. Seismicity of the Earth and Associated Phenomena[M]. 2nd ed. Princeton:Princeton University Press:1–310.
Mogi K. 1962. Study of elastic shocks caused by the fracture of heterogeneous materials and its relations to earthquake phenomena[J].Bull Earthq Res Inst,Univ Tokyo,40(1):125–173.
Mogi K. 1967. Regional variations in magnitude-frequency relation of earthquakes[J]. Bull Earthq Res Inst,Univ Tokyo,45(2):313 –325.
Nakaya S. 2006. Spatio-temporal variation in b value within the subducting slab prior to the 2003 Tokachi-Oki earthquake(M8.0),Japan[J]. J Geophys Res,111(B3):B03311.
Nuannin P,Kulhánek O,Persson L. 2012. Variations of b-values preceding large earthquakes in the Andaman-Sumatra subduction zone[J]. J Asian Earth Sci,61:237–242.
Papazachos B C. 1974. Dependence of the seismic parameter b on the magnitude range[J]. Pure Appl Geophys,112(6):1059–1065.
Rydelek P A,Sacks I S. 1989. Testing the completeness of earthquake catalogues and the hypothesis of self-similarity[J].Nature,337(6204):251–253.
Scholz C H. 1968. The frequency-magnitude relation of microfracturing in rock and its relation to earthquakes[J]. Bull Seismol Soc Am,58(9):399–415.
Schorlemmer D,Wiemer S,Wyss M,Jackson D D. 2004. Earthquake statistics at Parkfield:2. Probabilistic forecasting and testing[J]. J Geophys Res,109(B12):B12308.
Schorlemmer D,Wiemer S,Wyss M. 2005. Variations in earthquake-size distribution across different stress regimes[J]. Nature,434 (7058):539–542.
Shi Y L,Bolt B A. 1982. The standard error of the magnitude-frequency b value[J]. Bull Seismol Soc Am,72(5):1677–1687.
Smith W D. 1981. The b-value as an earthquake precursor[J]. Nature,289(5794):136–139.
Waldhauser F,Ellsworth W L. 2000. A double-difference earthquake location algorithm:Method and application to the northern Hayward fault,California[J]. Bull Seismol Soc Am,90(6):1353–1368.
Waldhauser F,Ellsworth W L. 2002. Fault structure and mechanics of the Hayward fault,California,from double-difference earthquake locations[J]. J Geophys Res,107(B3):ESE 3-1–ESE 3-15.
Wiemer S,Katsumata K. 1999. Spatial variability of seismicity parameters in aftershock zones[J]. J Geophys Res,104(B6):13135–13151.
Wiemer S,Wyss M. 2000. Minimum magnitude of completeness in earthquake catalogs:Examples from Alaska,the western United States,and Japan[J]. Bull Seismol Soc Am,90(4):859–869.
Wiemer S,Gerstenberge M,Hauksson E. 2002. Properties of the aftershock sequence of the 1999 MW7.1 Hector Mine earthquake:Implications for aftershock hazard[J]. Bull Seismol Soc Am,90(4):1227–1240.
Xu Z Q,Ji S C,Cai Z H,Zeng L S,Geng Q R,Cao H. 2012. Kinematics and dynamics of the Namche Barwa Syntaxis,eastern Himalaya:Constraints from deformation,fabrics and geochronology[J]. Gondwana Res,21(1):19–36.
Zeitler P K,Meltzer A S,Brown L,Kidd W S F,Lim C,Enkelmann E. 2014. Tectonics and topographic evolution of Namche Barwa and the easternmost Lhasa block,Tibet[G]//Toward an Improved Understanding of Uplift Mechanisms and the Elevation History of the Tibetan Plateau. Colorado:Geological Society of America,507:23–58.