1927年古浪8级大地震断层面参数和滑动性质
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摘要
1927年古浪发生8级大地震,此次地震给古浪及邻近地区造成了轻重不等的破坏。对这次地震的发震构造,前人的研究结果存在较大分歧。本研究根据成丛小震发生在大震断层面附近的原则及参考前人对该地震发震构造的认识,采用1985年到2012年发生在地震破裂区的精定位地震目录,选定了2个长条状研究区域,将模拟退火算法和高斯-牛顿算法结合,利用小震密集程度求解主震断层面的走向与倾角。在此基础上考虑区域构造应力参数,给出了已求得的断层面上的滑动角。然后结合已有的深部构造研究结果以及地表考察结果,简单讨论了此次地震的孕震环境和发震机制。文中反演到的断层1位于此次地震等震线的最高烈度(Ⅺ度)圈内,表明反演到的震源断层可能就是控制此次地震的发震构造。另外,首次发现在主干断裂中南部有1个小震成丛区,也能反演出1个断层,这可能是地震时震区整体发生了逆时针旋转而在主干断裂之上新发育的张性地震断层。
The Gulang M8.0 great earthquake occurred in 1927,many places in Gulang and adjacent areas had suffered destruction in various degrees. So far,divergences exist in the former studies on its seismogenic structure. It is known that clustered small earthquakes often occur in vicinities of fault plane of large earthquake. In this study,the precisely relocated earthquakes which occurred near the earthquake rupture zone between 1985 and 2012 are used,and two strip-shaped zones of clustered small earthquakes are chosen according to the previous studies of the causative structure of this earthquake. Based on the simulated annealing and Gauss-Newtonian nonlinear inversion algorithms,we obtained fault plane parameters of the earthquake such as strike,dip,and location using data of densely concentrated small events. On this condition,rake angles of the fault plane are further inferred from regional tectonic stress parameter. Then we discussed briefly the seismogenic environment and causal mechanism of the earthquake,combined with the results of deep tectonics and surface investigations. The focal fault we inverted locates within the meizoseismal area( intensity Ⅺ)of the Gulang M8.0 in 1927,suggesting that the focal fault obtained by inversion is possibly the causative structure of this earthquake. Besides,we found a clustered zone of small earthquakes near the south-central part of the main fault,and a fault plane could be derived from them,which we think might be a tensional seismic fault developed on the main fault when the whole earthquake-hit region rotated counterclockwise during the big earthquake.
The Gulang M8.0 great earthquake occurred in 1927,many places in Gulang and adjacent areas had suffered destruction in various degrees. So far,divergences exist in the former studies on its seismogenic structure. It is known that clustered small earthquakes often occur in vicinities of fault plane of large earthquake. In this study,the precisely relocated earthquakes which occurred near the earthquake rupture zone between 1985 and 2012 are used,and two strip-shaped zones of clustered small earthquakes are chosen according to the previous studies of the causative structure of this earthquake. Based on the simulated annealing and Gauss-Newtonian nonlinear inversion algorithms,we obtained fault plane parameters of the earthquake such as strike,dip,and location using data of densely concentrated small events. On this condition,rake angles of the fault plane are further inferred from regional tectonic stress parameter. Then we discussed briefly the seismogenic environment and causal mechanism of the earthquake,combined with the results of deep tectonics and surface investigations. The focal fault we inverted locates within the meizoseismal area( intensity Ⅺ)of the Gulang M8.0 in 1927,suggesting that the focal fault obtained by inversion is possibly the causative structure of this earthquake. Besides,we found a clustered zone of small earthquakes near the south-central part of the main fault,and a fault plane could be derived from them,which we think might be a tensional seismic fault developed on the main fault when the whole earthquake-hit region rotated counterclockwise during the big earthquake.
引文
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高祥林,罗焕炎.1992.大陆板内震源断层的特征[J].地震地质,14(3):260—263.GAO Xiang-lin,LUO Huan-yan.1992.Characteristics of seismic-source faults within the continental plate[J].Seismology and Geology,14(3):260—263(in Chinese).
顾功叙主编.1983.中国地震目录(公元1831年—公元1969年)[Z].北京:科学出版社.GU Gong-xu(ed).1983.Catalogue of Earthquakes in China(1831—1969)[Z].Science Press,Beijing(in Chinese).
国家地震局兰州地震研究所编.1989.甘肃省地震资料汇编[M].北京:地震出版社.Lanzhou Institute of Seismology,SSB.1989.Corpus of Earthquake Data in Gansu Province[M].Seismological Press,Beijing(in Chinese).
国家地震局兰州地震研究所,宁夏回族自治区地震队.1980.1920年海原大地震[M].北京:地震出版社.Lanzhou Institute of Seismology,Seismological Bureau of Ningxia Hui Autonomous Region.1980.The Haiyuan Great\sEarthquake in 1920[M].Seismological Press,Beijing(in Chinese).
郭安宁,郭增建.2010.从震源模式讨论2008年汶川8级地震的回顾性预测[J].地震地质,32(1):115—118.doi:10.3969/.jissn.0253-4967.2010.01.012.GUO An-ning,GUO Zeng-jian.2010.A discussion on the retrospective prediction of the MS8.0 Wenchuan earthquake\sin 2008 by means of earthquake source models[J].Seismology and Geology,32(1):115—118(in Chinese).
侯康明,邓起东,刘百篪,等.1998.1927年古浪8级大震破裂的三维数值理论模拟[J].西北地震学报,20(3):59—65.HOU Kang-ming,DENG Qi-dong,LIU Bai-chi,et al.1998.3-D numerical simulation of surface rupture caused by\sthe 1927 Gulang MS8 earthquake[J].Northwestern Seismological Journal,20(3):59—65(in Chinese).
胡新亮,刁桂苓,高景春,等.2002.用现今小震推断洪洞、临汾2次历史大震的震源断层[J].中国地震,18(1):76—85.HU Xin-liang,DIAO Gui-ling,GAO Jing-chun,et al.2002.Application of present small earthquakes to infer the focal\sfaults of two large historical earthquakes in Hongdong and Linfen,Shanxi Province[J].Earthquake Research inChina,18(1):76—85(in Chinese).
贾云鸿,陈志泰,戴华光,等.1988.1927年古浪地震断层特征及其与活动断层的关系[A].见:新疆维吾尔自治区地震局编.中国地震断层研究.乌鲁木齐:新疆人民出版社.JIA Yun-hong,CHEN Zhi-tai,DAI Hua-guang,et al.1988.The relationship of active fault and the characteristic of\sthe seismic fault of Gulang strong earthquake in 1927[A].In:Seismological Bureau of Xinjiang Uygur\sAutonomous Region(ed).The Studies of Chinese Seismic Faults.Xinjiang People's Publishing House,Urumqi(in\sChinese).
李海鸥,徐锡伟,马文涛.2011.天祝-古浪地区双差地震层析成像与古浪地震构造探讨[J].地震学报,33(2):156—164.LI Hai-ou,XU Xi-wei,MA Wen-tao.2011.Double-difference tomography in Tianzhu-Gulang region and discussion on\sseismotectonics of 1927 Gulang M8.0 earthquake[J].Acta Seismologica Sinica,33(2):156—164(in Chinese).
李文军.2004.用余震序列的数字地震资料对卢龙地区活动构造的研究[D].[学位论文].北京:中国地震局地球物理研究所.LI Wen-jun.2004.Study on tectonics of Lulong,eastern Heibei Province using digital seismic data of aftershocks[D].Ph D thesis.Institute of Geophysics,China Earthquake Administration,Beijing(in Chinese).
梁桂培,陈爱玲,何善康,等.1983.甘肃西部地区深部构造[J].西北地震学报,15(1):66—78.LIANG Gui-pei,CHEN Ai-ling,HE Shan-kang,et al.1983.The deep structure of the western region of Gansu\sProvince[J].Northwestern Seismological Journal,15(1):66—78(in Chinese).
刘白云,袁道阳,张波,等.2012.1879年武都南8级大地震断层面参数和滑动性质的厘定[J].地震地质,34(3):415—424.doi:10.3969/j.issn.0253-4967.2012.03.003.LIU Bai-yun,YUAN Dao-yang,ZHANG Bo,et al.2012.Determination of fault parameters and sliding behavior of the1879 southern Wudu 8.0 earthquake[J].Seismology and Geology,34(3):415—424(in Chinese).
刘白云,曾文浩,袁道阳,等.1954年腾格里沙漠北7级地震断层面参数和滑动性质研究[J].地震工程学报,36(3):622—627.doi:10.3969/j.issn.1000-0844.2014.03.0622.LIUBai-yun,ZENG Wen-hao,YUAN Dao-yang,et al.2014.Fault parameter and sliding behavior determination of the1954 northern Tenggeli desert M7.0 earthquake[J].China Earthquake Engineering Journal,36(3):622—627(in Chinese).
刘澜波,Zoback M D,陆燕萍,等.1995.美国新马德里地震带的震间应变积累[J].地球物理学报,38(6):757—766.LIU Lan-bo,Zoback M D,LU Yan-ping,et al.1995.Interseismic strain accumulation in the new Madrid seismic zone[J].Chinese Journal of Geophysics,38(6):757—766(in Chinese).
邵学钟,张家茹,章思亚,等.1993.邢台地震区深部构造背景的地震转换波探测和研究[J].地球物理学报,36(5):610—619.SHAO Xue-zhong,ZHANG Jia-ru,ZHANG Si-ya,et al.1993.Study of deep structures in Xingtai earthquake area by\smethod of converted waves of earthquakes[J].Chinese Journal of Geophysics,36(5):610—619(in Chinese).
万永革,沈正康,刁桂苓,等.2008.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[J].地球物理学报,51(3):793—804.WAN Yong-ge,SHEN Zheng-kang,DIAO Gui-ling,et al.2008.An algorithm of fault parameter determination using\sdistribution of small earthquakes and parameters of regional stress field and its application to Tangshan earthquake\ssequence[J].Chinese Journal of Geophysics,51(3):793—804(in Chinese).
王鸣,王培德.1992.1989年10月18日大同-阳高地震的震源机制和发震构造[J].地震学报,14(4):407—415.WANG Ming,WANG Pei-de.1992.The mechanism and seismogenic structure of Datong-Yanggao earthquake whichoccurred on 0ct.18,1989[J].Acta Seismologica Sinica,14(4):407—415(in Chinese).
王泽皋.1985.大震区的“长期活动”[J].地震学报,7(3):254—266.WANG Ze-gao.1985.The“long-term activity”of large seismic regions[J].Acta Seismologica Sinica,7(3):254—266(in Chinese).
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