宁洱地震区深部电性结构及发震构造初析(一)
|
摘要
在2007年6月3日宁洱6.4级地震区进行了宽频带(1000～1/4096Hz)大地电磁观测,采用了远参考道技术和Robust技术对观测数据进行了处理,分析了视电阻率和相位曲线、二维偏离度及区域电性结构方向,采用非线性共扼梯度(NLCG)二维反演技术对实测资料进行了反演,得到了与实测曲线拟合程度较高的反演模型。从二维解释结果可以看出:横向上,以12号测点为界,明显地划分为2个不同的电性分区,推测存在具一定延伸的断裂构造。纵向上,30km深度以上大致可分为4个电性层:1)中、新生代盆地沉积层(Mz—Cz),厚约1km。2)古生代沉积层(Pz),厚约5km。3)壳内高导层(HCL)。4)中、下地壳(MLC)。其中壳内高导层埋深在12号点左右存在较大的差异,推测在12—13号点下高导层顶部存在壳内的滑脱构造。宁洱地震震源深度为5km,文中所推测的滑脱构造位于这一层位上。认为该滑脱构造为本次地震的发震构造。
Magnetotelluric data have recently been obtained at 9 sites along a profile of about 8km long and orientated approximately E-W in the Ning'er earthquake area which lies in southwestern Yunnan province.From these data,the high-resolution apparent resistivity,impedance phase curves,skewnesses and regional strike were calculated by using the remote reference technique and robust data processing technique,and then analyzed.The 2-D inversion method NLCG was used for data interpretation.According to the 2-D electrical structure of Ning'er seismic area,there may be an extended fault because of an obvious different electrical structure between the left & right side of the site 12.On longitudinal distribution,the crust of this area can be divided into four electrical layers:1)Mesozoic and Cenozoic sediments,about 1km,2)Paleozoic sediment,about 5km,3)high conductive layers in crust,and 4)middle and lower crust.A high conductive layer exists in the crust of the area.Between the site 12 and 13,there might be a decollement structure on top of high conductive layer under them,because the buried depth of the layer is quite different between the left & right side of the site 12.Focal depth of the Ning'er earthquake is about 5km,the decollement structure presumed in this research lies in this layer,and its strike is NW,same as that of the major axis direction of the isoseismal curve of this earthquake.So we conclude that the decollement structure is the seismogenic structure.
Magnetotelluric data have recently been obtained at 9 sites along a profile of about 8km long and orientated approximately E-W in the Ning'er earthquake area which lies in southwestern Yunnan province.From these data,the high-resolution apparent resistivity,impedance phase curves,skewnesses and regional strike were calculated by using the remote reference technique and robust data processing technique,and then analyzed.The 2-D inversion method NLCG was used for data interpretation.According to the 2-D electrical structure of Ning'er seismic area,there may be an extended fault because of an obvious different electrical structure between the left & right side of the site 12.On longitudinal distribution,the crust of this area can be divided into four electrical layers:1)Mesozoic and Cenozoic sediments,about 1km,2)Paleozoic sediment,about 5km,3)high conductive layers in crust,and 4)middle and lower crust.A high conductive layer exists in the crust of the area.Between the site 12 and 13,there might be a decollement structure on top of high conductive layer under them,because the buried depth of the layer is quite different between the left & right side of the site 12.Focal depth of the Ning'er earthquake is about 5km,the decollement structure presumed in this research lies in this layer,and its strike is NW,same as that of the major axis direction of the isoseismal curve of this earthquake.So we conclude that the decollement structure is the seismogenic structure.
引文
陈海泓,郝杰.1993.云南思茅地区新生代的持续旋转[J].科学通报,21(1):2269—2272.CHEN Hai-hong,HAO Jie.1993.The lasting rotation of Simao area in Yunnan province during Cenozoic[J].ChineseScience Bulletin,21(1):2269—2272(in Chinese).
陈乐寿,王光锷.1990.大地电磁测深法[M].北京:地质出版社.CHEN Le-shou,WANG Guang-e.1990.Magnetotelluric Sounding Methods[M].Geological Publishing House,Bei-jing(in Chinese).
邓起东,张培震.2003.中国活动构造图(1∶400万)[Z].北京:地震出版社.DENG Qi-dong,ZHANG Pei-zhen.2003.Map of Active Tectonics in China[Z].Seismological Press,Beijing(in Chi-nese).
樊耀新.1998.思普地区地震活动和地质构造的相关性研究[J].地震研究,21(1):65—70.FAN Yao-xin.1998.A study on correlativity between seismicity and geological tectonics in Simao-Puer region[J].Journal of Seismological Research,21(1):65—70(in Chinese).
虢顺民,计凤桔,向宏发,等.2001.红河活动断裂带[M].北京:海洋出版社.GUO Shun-min,JI Feng-ju,XIANG Hong-fa,et al.2001.The Honghe Active Fault Zone[M].China Ocean Press,Beijing(in Chinese).
虢顺民,汪洋,计凤桔.1999.云南思茅—普洱地区中强震群发生的构造机制[J].地震地质,22(2):105—115.GUO Shun-min,WANG Yang,JI Feng-ju.1999.Tectonic mechanism of moderate-strong swarms in Yunnan s Simao-Pu er region[J].Seismology and Geology,22(2):105—115(in Chinese).
林中洋,胡鸿翔,张文彬,等.1993.滇西地区地壳上地幔速度结构特征的研究[J].地震学报,15(4):427—440.LIN Zhong-yang,HUHong-xiang,ZHANG Wen-bin,et al.1993.The preliminary interpretation of deep seismic sound-ing in western Yunnan[J].Acta Seismologica Sinica,15(4):427—440(in Chinese).
刘国栋,陈乐寿主编.1984.大地电磁测深研究[M].北京:地震出版社.LIU Guo-dong,CHEN Le-shou(ed).1984.Research of Magnetotelluric Sounding[M].Seismological Press,Beijing(in Chinese).
刘祖荫,苏有锦,秦嘉政,等.2002.20世纪云南地震活动[M].北京:地震出版社.LIU Zu-yin,SU You-jin,QIN Jia-zheng,et al.2002.Seismicity in Yunnan in the20th Century[M].SeismologicalPress,Beijing(in Chinese).
苗崇刚,胡永龙,周光全,等.2007.云南宁洱6.4级地震应急行动及灾害特征[J].国际地震动态,(6):5—11.MIAO Chong-gang,HU Yong-long,ZHOU Guang-quan,et al.2007.The emergency action and disaster characters ofNing erM6.4earthquake in Yunnan[J].Recent Developments in World Seismology,(6):5—11(in Chinese).
石应俊.1985.大地电磁测深法教程[M].北京:地震出版社.SHI Ying-jun.1985.Tutorial of Magnetotelluric Method[M].Seismological Press,Beijing(in Chinese).
汤吉,詹艳,赵国泽,等.2005.青藏高原东北缘玛沁—兰州—靖边剖面地壳上地幔电性结构研究[J].地球物理学报,48(5):1205—1216.TANG Ji,ZHAN Yan,ZHAO Guo-ze,et al.2005.Electrical conductivity structure of the crust and upper mantle in thenortheastern margin of the Qinghai-Tibet plateau along the profile Maqin-Lanzhou-Jingbian[J].Acta GeophysicaSinica,48(5):1205—1216(in Chinese).
张智,赵兵,张晰,等.2006.云南思茅—中旬地震剖面的地壳结构[J].地球物理学报,49(5):1377—1384.ZHANG Zhi,ZHAO Bing,ZHANG Xi,et al.2006.Crustal structure beneath the wide-angle seismic profile betweenSimao and Zhongdian in Yunnan[J].Acta Geophysica Sinica,49(5):1377—1384(in Chinese).
朱成男,周瑞琦.1981.普洱磨黑6.8级地震区地质构造基本特征[J].地震研究,4(1):69—77.ZHU Cheng-nan,ZHOU Rui-qi.1981.Basic characteristics of both the geology and structure in the epicenter and itssurrounding area of1979earthquake(M=6.8)in Puer-Mohei[J].Journal of Seismological Research,4(1):69—77(in Chinese).
詹艳,赵国泽,陈小斌,等.2004.宁夏海原大震区安州—韦州剖面大地电磁探测与研究[J].地球物理学报,47(2):274—281.ZHAN Yan,ZHAO Guo-ze,CHEN Xiao-bin,et al.2004.Crust structure from magnetotelluric profiling in the Haiyuanearthquake area in Ningxia Hui Autonomous Region[J].Acta Geophysica Sinica,47(2):274—281(in Chi-nese).
赵国泽,刘国栋,詹艳,等.1998.张北—尚义地震区及其邻区地壳上地幔结构[J].地震地质,21(2):155—163.ZHAO Guo-ze,LIU Guo-dong,ZHAN Yan,et al.1998.The structure of the crust and upper mantle for the Zhangbei-Shangyi seismic area and its neighboring region[J].Seismology and Gology,21(2):155—163(in Chinese).
赵国泽,刘铁胜,江钊,等.1997.山西阳高—河北容城剖面大地电磁资料的二维反演解释[J].地球物理学报,40(1):38—48.ZHAO Guo-ze,LIU Tie-sheng,JIANG Zhao,et al.1997.Investigation on MTdata along Yanggao-Rongcheng profile bytwo-dimensional inversion[J].Acta Geophysica Sinica,40(1):38—48(in Chinese).
赵国泽,汤吉,詹艳,等.2004.青藏高原东北缘地壳电性结构和地块变形关系的研究[J].中国科学(D辑),34(10):908—918.ZHAO Guo-ze,TANG Ji,ZHAN Yan,et al.2004.Relation between electricity structure of the crust and deformation ofcrustal blocks on the northeastern margin of Qinghai-Tibet plateau[J].Science in China(Ser D),34(10):908—918(in Chinese).
Berdichevsky M N,Dmitriev VⅠ,Pozdnjakova E E.1998.On two-dimensional interpretation of magnetotelluricsoundings[J].Geophys J Int,133:585—606.
Egbert G D.1997.Robust multiple-station magnetotelluric data processing[J].Geophys J Int,130:475—496.
Gambel TD,Goubau W M,Clarke J.1979.Magnetotelluric data processing[J].Geophys,44:53—68.
Leod J.2005.2-D versus3-D magnetotelluric data interpretation[J].Surveys in Geophysics,26:511—543.
Leod J,Queralt P,Marti A,et al.2002.Two-dimensional interpretation of three-dimensional magnetotelluric data:anexample of limitations and resolution[J].Geophys J Int,150:127—139.
Rodi W,Mackie R L.2001.Nonlinear conjugate gradients algorithm for2-D magnetotelluric inversion[J].Geophys-ics,66(1):174—187.
Wannamaker P E,Hohmann G W,Ward S H.1984.Magnetotelluric responses of three-dimensional bodies in layeredearths[J].Geophysics,49(9):1517—1533.
陈乐寿,王光锷.1990.大地电磁测深法[M].北京:地质出版社.CHEN Le-shou,WANG Guang-e.1990.Magnetotelluric Sounding Methods[M].Geological Publishing House,Bei-jing(in Chinese).
邓起东,张培震.2003.中国活动构造图(1∶400万)[Z].北京:地震出版社.DENG Qi-dong,ZHANG Pei-zhen.2003.Map of Active Tectonics in China[Z].Seismological Press,Beijing(in Chi-nese).
樊耀新.1998.思普地区地震活动和地质构造的相关性研究[J].地震研究,21(1):65—70.FAN Yao-xin.1998.A study on correlativity between seismicity and geological tectonics in Simao-Puer region[J].Journal of Seismological Research,21(1):65—70(in Chinese).
虢顺民,计凤桔,向宏发,等.2001.红河活动断裂带[M].北京:海洋出版社.GUO Shun-min,JI Feng-ju,XIANG Hong-fa,et al.2001.The Honghe Active Fault Zone[M].China Ocean Press,Beijing(in Chinese).
虢顺民,汪洋,计凤桔.1999.云南思茅—普洱地区中强震群发生的构造机制[J].地震地质,22(2):105—115.GUO Shun-min,WANG Yang,JI Feng-ju.1999.Tectonic mechanism of moderate-strong swarms in Yunnan s Simao-Pu er region[J].Seismology and Geology,22(2):105—115(in Chinese).
林中洋,胡鸿翔,张文彬,等.1993.滇西地区地壳上地幔速度结构特征的研究[J].地震学报,15(4):427—440.LIN Zhong-yang,HUHong-xiang,ZHANG Wen-bin,et al.1993.The preliminary interpretation of deep seismic sound-ing in western Yunnan[J].Acta Seismologica Sinica,15(4):427—440(in Chinese).
刘国栋,陈乐寿主编.1984.大地电磁测深研究[M].北京:地震出版社.LIU Guo-dong,CHEN Le-shou(ed).1984.Research of Magnetotelluric Sounding[M].Seismological Press,Beijing(in Chinese).
刘祖荫,苏有锦,秦嘉政,等.2002.20世纪云南地震活动[M].北京:地震出版社.LIU Zu-yin,SU You-jin,QIN Jia-zheng,et al.2002.Seismicity in Yunnan in the20th Century[M].SeismologicalPress,Beijing(in Chinese).
苗崇刚,胡永龙,周光全,等.2007.云南宁洱6.4级地震应急行动及灾害特征[J].国际地震动态,(6):5—11.MIAO Chong-gang,HU Yong-long,ZHOU Guang-quan,et al.2007.The emergency action and disaster characters ofNing erM6.4earthquake in Yunnan[J].Recent Developments in World Seismology,(6):5—11(in Chinese).
石应俊.1985.大地电磁测深法教程[M].北京:地震出版社.SHI Ying-jun.1985.Tutorial of Magnetotelluric Method[M].Seismological Press,Beijing(in Chinese).
汤吉,詹艳,赵国泽,等.2005.青藏高原东北缘玛沁—兰州—靖边剖面地壳上地幔电性结构研究[J].地球物理学报,48(5):1205—1216.TANG Ji,ZHAN Yan,ZHAO Guo-ze,et al.2005.Electrical conductivity structure of the crust and upper mantle in thenortheastern margin of the Qinghai-Tibet plateau along the profile Maqin-Lanzhou-Jingbian[J].Acta GeophysicaSinica,48(5):1205—1216(in Chinese).
张智,赵兵,张晰,等.2006.云南思茅—中旬地震剖面的地壳结构[J].地球物理学报,49(5):1377—1384.ZHANG Zhi,ZHAO Bing,ZHANG Xi,et al.2006.Crustal structure beneath the wide-angle seismic profile betweenSimao and Zhongdian in Yunnan[J].Acta Geophysica Sinica,49(5):1377—1384(in Chinese).
朱成男,周瑞琦.1981.普洱磨黑6.8级地震区地质构造基本特征[J].地震研究,4(1):69—77.ZHU Cheng-nan,ZHOU Rui-qi.1981.Basic characteristics of both the geology and structure in the epicenter and itssurrounding area of1979earthquake(M=6.8)in Puer-Mohei[J].Journal of Seismological Research,4(1):69—77(in Chinese).
詹艳,赵国泽,陈小斌,等.2004.宁夏海原大震区安州—韦州剖面大地电磁探测与研究[J].地球物理学报,47(2):274—281.ZHAN Yan,ZHAO Guo-ze,CHEN Xiao-bin,et al.2004.Crust structure from magnetotelluric profiling in the Haiyuanearthquake area in Ningxia Hui Autonomous Region[J].Acta Geophysica Sinica,47(2):274—281(in Chi-nese).
赵国泽,刘国栋,詹艳,等.1998.张北—尚义地震区及其邻区地壳上地幔结构[J].地震地质,21(2):155—163.ZHAO Guo-ze,LIU Guo-dong,ZHAN Yan,et al.1998.The structure of the crust and upper mantle for the Zhangbei-Shangyi seismic area and its neighboring region[J].Seismology and Gology,21(2):155—163(in Chinese).
赵国泽,刘铁胜,江钊,等.1997.山西阳高—河北容城剖面大地电磁资料的二维反演解释[J].地球物理学报,40(1):38—48.ZHAO Guo-ze,LIU Tie-sheng,JIANG Zhao,et al.1997.Investigation on MTdata along Yanggao-Rongcheng profile bytwo-dimensional inversion[J].Acta Geophysica Sinica,40(1):38—48(in Chinese).
赵国泽,汤吉,詹艳,等.2004.青藏高原东北缘地壳电性结构和地块变形关系的研究[J].中国科学(D辑),34(10):908—918.ZHAO Guo-ze,TANG Ji,ZHAN Yan,et al.2004.Relation between electricity structure of the crust and deformation ofcrustal blocks on the northeastern margin of Qinghai-Tibet plateau[J].Science in China(Ser D),34(10):908—918(in Chinese).
Berdichevsky M N,Dmitriev VⅠ,Pozdnjakova E E.1998.On two-dimensional interpretation of magnetotelluricsoundings[J].Geophys J Int,133:585—606.
Egbert G D.1997.Robust multiple-station magnetotelluric data processing[J].Geophys J Int,130:475—496.
Gambel TD,Goubau W M,Clarke J.1979.Magnetotelluric data processing[J].Geophys,44:53—68.
Leod J.2005.2-D versus3-D magnetotelluric data interpretation[J].Surveys in Geophysics,26:511—543.
Leod J,Queralt P,Marti A,et al.2002.Two-dimensional interpretation of three-dimensional magnetotelluric data:anexample of limitations and resolution[J].Geophys J Int,150:127—139.
Rodi W,Mackie R L.2001.Nonlinear conjugate gradients algorithm for2-D magnetotelluric inversion[J].Geophys-ics,66(1):174—187.
Wannamaker P E,Hohmann G W,Ward S H.1984.Magnetotelluric responses of three-dimensional bodies in layeredearths[J].Geophysics,49(9):1517—1533.
版权所有：© 2023 中国地质图书馆 中国地质调查局地学文献中心