岷县漳县6.6级地震前区域地壳运动变形背景与断层形变异常特征
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摘要
利用甘肃岷县漳县6.6级地震区所在的青藏块体东北缘地区的区域水准、GPS、流动重力和跨断层短测线等地形变监测资料,结合地质构造、动力环境和已往的研究结果,分析了不同类型资料反映的震前区域性地壳变形背景、断层形变异常特征和可能的机理。结果认为:(1)岷县漳县6.6级地震前西秦岭、六盘山等构造区不同程度地存在着GPS水平挤压闭锁高应变积累、垂直隆升异常高梯度带和重力升、降差异剧烈变化等中长期背景;(2)震前到震时发震断裂附近及其外围相关构造区域断层形变异常在空间和时间上的起伏波动变化显著,尤其是汶川地震以来的波动变化在一定程度上反映了与本区构造比邻的龙门山断裂带剧烈右旋错动对本区的影响,与本次岷县6.6级地震过程有关;(3)本区有地形变监测资料积累以来缺乏6级以上震例,虽然存在不同程度的中长期形变背景异常,但何时进入短期-短临阶段确实很难把握,需要不断积累总结和探索提高。
In this study,the regional crustal movement background is analyzed using various types of regional crustal deformation data including vertical deformation,GPS,mobile gravity,and cross-fault short line observation in the Minxian-Zhangxian MS6.6 earthquake zone located at the northeastern margin of the Qinghai-Tibet block.On the basis of regional geological structures,dynamic environment,and existing research findings,the anomaly characteristics of crossfault deformation and its possible mechanism also are discussed.The results show varying degrees of medium-and long-term seismogenic backgrounds in the west Qinling and Liupanshan tectonic province such as a GPS horizontal compresso-locked zone with high strain accumulation and an anomalous GPS vertical uplift belt with a high gradient,in addition to an abrupt change in the pull of gravity prior to the Minxian-Zhangxian earthquake.Moreover,a fault deformation anomaly near the Lintan-Minxian fault caused the earthquake,and its peripheral-related structure realm showed significant temporal and spatial fluctuation up to the time of the earthquake.Particularly since the Wenchuan MS8.0earthquake,the abnormal fluctuations of cross-fault deformation have reflect that the influences from the active dextral rupture of Longmen Mountain seismogenic structure adjacent to the regional tectonic belt have promoted the formation of this tectonic province and the seismogenic process of the Minxian-Zhangxian earthquake.Further,varying degrees of medium-and long-term seismogenic backgrounds exist in the area;therefore,it is difficult to determine the impending earthquake stage because few earthquakes above 6have occurred since the data of crustal deformation in this region has been accumulated.Nonetheless,earthquake data must be continually accumulated,evaluated,and improved.
In this study,the regional crustal movement background is analyzed using various types of regional crustal deformation data including vertical deformation,GPS,mobile gravity,and cross-fault short line observation in the Minxian-Zhangxian MS6.6 earthquake zone located at the northeastern margin of the Qinghai-Tibet block.On the basis of regional geological structures,dynamic environment,and existing research findings,the anomaly characteristics of crossfault deformation and its possible mechanism also are discussed.The results show varying degrees of medium-and long-term seismogenic backgrounds in the west Qinling and Liupanshan tectonic province such as a GPS horizontal compresso-locked zone with high strain accumulation and an anomalous GPS vertical uplift belt with a high gradient,in addition to an abrupt change in the pull of gravity prior to the Minxian-Zhangxian earthquake.Moreover,a fault deformation anomaly near the Lintan-Minxian fault caused the earthquake,and its peripheral-related structure realm showed significant temporal and spatial fluctuation up to the time of the earthquake.Particularly since the Wenchuan MS8.0earthquake,the abnormal fluctuations of cross-fault deformation have reflect that the influences from the active dextral rupture of Longmen Mountain seismogenic structure adjacent to the regional tectonic belt have promoted the formation of this tectonic province and the seismogenic process of the Minxian-Zhangxian earthquake.Further,varying degrees of medium-and long-term seismogenic backgrounds exist in the area;therefore,it is difficult to determine the impending earthquake stage because few earthquakes above 6have occurred since the data of crustal deformation in this region has been accumulated.Nonetheless,earthquake data must be continually accumulated,evaluated,and improved.
引文
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[5]蔡副全.1879年武都南8级地震新资料的发现与应用[J].地震工程学报,2013,35(2):311-320.CAI Fu-quan.New Discovery and Application of Some Historical Data for the M8.0Earthquake in Southern Wudu in 1879[J].China Earthquake Engineering Journal,2013,35(2):311 -320.(in Chinese)
[6]王双绪,张希,祝意青,等.南北地震带北段强震形变异常特征与预测指标研究[J].西北地震学报,2012,34(2):105-113.WANG Shuang-xu,ZHANG Xi,THU Yi-qing,et al.Study on the Characteristics of Strong Earthquake Deformation Anomalies and Forecasting Index in the North Segment of the south-north Seismic Belt of China[J].Northwestern Seismological Journal,2012,34(2):105-113.(in Chinese)
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[8]江在森,刘经南.应用最小二乘配置建立地壳运动速度场与应变场的方法[J].地球物理学报,2010,53(5):11091-117.JIANG Zai-sen,LIU Jing-nan.The Method in Establishing Strain Field and Velocity Field of Crustal Movement UsingLeast Squares Collocation.Chinese J.Geophys.[J].2010,53 (5):1109-1117.(in Chinese)
[9]万永革,沈正康,盛书中,等.2008年汶川大地震对周围断层的影响[J].地震学报,2009,31(2):128-139.WAN Yong-ge,SHEN Zheng-kang,SHENG Shu-zhong,et al.The Influence of 2008 Wenchuan Earthquake Onsurrounding Faults[J].Acta Seismologica Sinica,2009,31(2):128-139 .(in Chinese)
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[11]王双绪,江在森.丽江7.0级和唐山7.8级地震前形变场动态演化与异常特征[J].地壳形变与地震,1997,17(4):40-45 .WANG Shuang-xu,JIANG Zai-sen.Dynamic Evolution and Abnormal Character of Deformation Field before Lijiang MS7 .0and Tangshan MS7 .8Earthquakes[J].Crustal Deformation and Earthquake,1997,17(4):40-45.(in Chinese)
[12]Zhu Y,Zhan F B,Zhou J,et a1.Gravity Measurements and Their Variations before the 2008 Wenchuan Earthquake[J].BSSA,2010,100(5B):2815-2824.
[13]祝意青,刘芳,付广裕,等.汶川地震前后青藏高原东北缘重力场动态变化研究[J].地震,2012,32(2),88-94.ZHU Yi-qing,LIU Fang,FU Guang-yu,et al.Gavity Changes before and after the Wenchuan MS8 .0Earthquake in The Northeastern Edge of Qinghai-Tibet Block[J].Earthquake,2012,32(2),88-94.(in Chinese)
[14]徐纪人,姚立询,汪进.1986年8月26日门源6.4级地震及其强余震的震源机制解[J].西北地震学报,1986,8(4):82-84 .XU Ji-ren,YAO Li-xun,WANG Jin.The Focal-mechanism Solutions of the Menyuan MS6 .4Earthquake and Strong Aftershock on aug.26,1986[J].Northwestern Seismological Journal,1986,8(4):82-84.(in Chinese)
[15]温增平.1990年10月20日天祝、古浪6.2级地震的震源机制[J].西北地震学报,1991,13(1):81.WEN Zeng-ping.The Focal-mechanism Solutions of the Tianzhu-Jingtai MS6 .2Earthquake on oct.20,1990[J].Northwestern Seismological Journal,1991,13(1):81.(in Chinese)
[2]江在森,丁平,王双绪,等.中国西部大地形变监测与地震预测[M].北京:地震出版社,2001.JIANG Zai-sen,DING Ping,WANG Shuang-xu,et al.Geodetic Deformation Monitoring and Earthquake Prediction of the West China[M].Beijing:Seismological Press,2001.(in Chinese)
[3]丁国瑜,卢演俦.中国岩石圈动力学概论[M].北京:地震出版社.1991.DING Guo-yu,LU Yan-chou.Introduction to Lithospheric Dynamics of China[M].Beijing:Seismological Press,1991.(in Chinese)
[4]刘小凤,梅秀苹,冯建刚,等.青藏高原北部地区地震基本活动状态定量评价[J].西北地震学报,2011,33(2):130-136.LU Xiao-feng,MEI Xiu-ping,FENG Jian-gang,et al.Quantitative Estimating Basic State of Seismicity in Northern Region of Qinghai-Xizang Plateau[J].Northwestern Seismological Journal,2011,33(2):130-136.(in Chinese)
[5]蔡副全.1879年武都南8级地震新资料的发现与应用[J].地震工程学报,2013,35(2):311-320.CAI Fu-quan.New Discovery and Application of Some Historical Data for the M8.0Earthquake in Southern Wudu in 1879[J].China Earthquake Engineering Journal,2013,35(2):311 -320.(in Chinese)
[6]王双绪,张希,祝意青,等.南北地震带北段强震形变异常特征与预测指标研究[J].西北地震学报,2012,34(2):105-113.WANG Shuang-xu,ZHANG Xi,THU Yi-qing,et al.Study on the Characteristics of Strong Earthquake Deformation Anomalies and Forecasting Index in the North Segment of the south-north Seismic Belt of China[J].Northwestern Seismological Journal,2012,34(2):105-113.(in Chinese)
[7]李瑞莎,张希,唐红涛,等.玉门、民乐等地震前跨断层形变异常及与定点前兆观测的相互印证[J].西北地震学报,2012,34(4):388-392.LI Rui-sha,ZHANG Xi,THANG Hong-tao,et al.Crossfault Deformation Anomaly and Confirm Each Other with the Fixed-point Precursors Observation before Yumen and Minle Earthquakes[J].Northwestern Seismological Journal,2012,34 (4):388-392.(in Chinese)
[8]江在森,刘经南.应用最小二乘配置建立地壳运动速度场与应变场的方法[J].地球物理学报,2010,53(5):11091-117.JIANG Zai-sen,LIU Jing-nan.The Method in Establishing Strain Field and Velocity Field of Crustal Movement UsingLeast Squares Collocation.Chinese J.Geophys.[J].2010,53 (5):1109-1117.(in Chinese)
[9]万永革,沈正康,盛书中,等.2008年汶川大地震对周围断层的影响[J].地震学报,2009,31(2):128-139.WAN Yong-ge,SHEN Zheng-kang,SHENG Shu-zhong,et al.The Influence of 2008 Wenchuan Earthquake Onsurrounding Faults[J].Acta Seismologica Sinica,2009,31(2):128-139 .(in Chinese)
[10]王双绪,江在森,唐传芬.兰天武地区现今大地垂直形变场演化与地壳运动特征[J].地壳形变与地震,1995,15(1):62-70 .WANG Shuang-xu,JIANG Zai-sen,TANG Chuan-fen.Characteristics of the Evolution of Recent Vertical Deformation Field and the Crustal Movement in Lanzhou-TianshuiWudu Area[J].Crustal Deformation and Earthquake,1995,15 (1):62-70.(in Chinese)
[11]王双绪,江在森.丽江7.0级和唐山7.8级地震前形变场动态演化与异常特征[J].地壳形变与地震,1997,17(4):40-45 .WANG Shuang-xu,JIANG Zai-sen.Dynamic Evolution and Abnormal Character of Deformation Field before Lijiang MS7 .0and Tangshan MS7 .8Earthquakes[J].Crustal Deformation and Earthquake,1997,17(4):40-45.(in Chinese)
[12]Zhu Y,Zhan F B,Zhou J,et a1.Gravity Measurements and Their Variations before the 2008 Wenchuan Earthquake[J].BSSA,2010,100(5B):2815-2824.
[13]祝意青,刘芳,付广裕,等.汶川地震前后青藏高原东北缘重力场动态变化研究[J].地震,2012,32(2),88-94.ZHU Yi-qing,LIU Fang,FU Guang-yu,et al.Gavity Changes before and after the Wenchuan MS8 .0Earthquake in The Northeastern Edge of Qinghai-Tibet Block[J].Earthquake,2012,32(2),88-94.(in Chinese)
[14]徐纪人,姚立询,汪进.1986年8月26日门源6.4级地震及其强余震的震源机制解[J].西北地震学报,1986,8(4):82-84 .XU Ji-ren,YAO Li-xun,WANG Jin.The Focal-mechanism Solutions of the Menyuan MS6 .4Earthquake and Strong Aftershock on aug.26,1986[J].Northwestern Seismological Journal,1986,8(4):82-84.(in Chinese)
[15]温增平.1990年10月20日天祝、古浪6.2级地震的震源机制[J].西北地震学报,1991,13(1):81.WEN Zeng-ping.The Focal-mechanism Solutions of the Tianzhu-Jingtai MS6 .2Earthquake on oct.20,1990[J].Northwestern Seismological Journal,1991,13(1):81.(in Chinese)
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