长江三峡水库诱发地震加密观测及地震成因初步分析
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摘要
从2009年3月起在长江三峡水库湖北段建立了26个地震台站组成的加密台网。2009年3—12月记录到2995次ML-0.8～2.9地震。利用双差定位软件重新确定了2837次地震的精确位置。结果显示:长江三峡水库库区小震震群分布图像呈线性分布或团块状丛集分布,团块状丛集一般在距离库水边5km范围内,地震线性分布可以延伸到距库水边16km远的地方;长江三峡水库湖北段地震主要集中分布在香溪河附近的仙女山断裂北端及九湾溪断裂、泄滩乡以西的长江两岸和巴东北岸神龙溪及附近地区,震源深度<10km,平均在4km左右;库区地震活动频次与库水位升降过程正相关,说明属于水库诱发地震。巴东库区神龙溪两岸地震明显呈现出3条线性分布,通过对比该地区碳酸盐岩的分布特征,发现是由于水库蓄水后,库水从神龙溪两岸等地下暗河渗入而诱发地震的;而仙女山断裂过江段、九湾溪断裂和泄滩乡、沙镇溪镇西部地区等的地震可能与仙女山断裂带、牛口断裂或顺层解理等不连续结构面软化,导致岩体失稳而诱发了水库地震,但诱发机制仍需要进一步详细研究才能获得令人信服的结论。另外,在秭归县文化南和杨林、巴东县东壤口镇以东等地存在着煤矿开采引起的矿山诱发地震,在长江三峡库区两岸存在着一些塌陷地震。
In accordance with the requirements of "Eleventh Five-Year" national scientific and technological support projects,an intensive seismic observation network consisting of 26 seismic stations was established at the Three Gorges Reservoir area in the section of Hubei Province in March 2009(21 short-period seismographs,5 broadband digital seismographs).From March to December,2009,2995 ML-0.8～2.9 earthquakes were observed during the trial impounding of the Three Gorges Reservoir(water level rose from 145m to 172.8m).Using the double difference earthquake location algorithm,2837 earthquakes were relocated precisely.The results show: The pattern of small local earthquake swarms in Three Gorges Reservoir area took on a linear distribution or mass-like cluster distribution,the mass-like clusters of events were generally within the distance of 5km from waterfront,and the linear distribution of the earthquakes could be extended to a distance of 16 kilometers away from waterfront.In Hubei section of Three Gorges Reservoir,earthquakes were mainly concentrated in the northern end of Xiannüfeng and Jiuwanxi Fault in the vicinity of the Xiangxihe river,and along the banks of the Yangtze river at the east of Xietan village and at Shenlongxi area on the northern bank in Badong region;the focal depths were less than 10km,and 4km in average.Earthquake frequency of the reservoir region had a positive correlation with reservoir water level fluctuation,indicating that the seismicity belonged to the reservoir induced earthquakes.Along the Shenlong river in the reservoir area,earthquakes showed three linear distributions in the northern Badong County,which was related to karst distribution.There are underground rivers along carbonate strata.When reservoir was impounded,water permeated into the underground rivers,thus inducing earthquakes.Earthquakes in the areas on the cross-river segment of Xiannüfeng Fault,the Jiuwanxi Fault and at the areas west of Xietan,Shazhen and Xizhen,may be related to the softening of discontinuities,such as the Nukou Fault,the Xiannüfeng Fault or the bedding joints,etc.,which would lead to failure of rock masses,thus,inducing earthquakes.However,convincing conclusions about the triggering mechanism still need further study.In addition,in the areas south of Wenhua and Yanglin of Zigui County and at Rangkou town east of Badong county,there are mining-induced earthquakes at the mines nearby.And on the shores of the reservoir,there are some collapse earthquakes.
In accordance with the requirements of "Eleventh Five-Year" national scientific and technological support projects,an intensive seismic observation network consisting of 26 seismic stations was established at the Three Gorges Reservoir area in the section of Hubei Province in March 2009(21 short-period seismographs,5 broadband digital seismographs).From March to December,2009,2995 ML-0.8～2.9 earthquakes were observed during the trial impounding of the Three Gorges Reservoir(water level rose from 145m to 172.8m).Using the double difference earthquake location algorithm,2837 earthquakes were relocated precisely.The results show: The pattern of small local earthquake swarms in Three Gorges Reservoir area took on a linear distribution or mass-like cluster distribution,the mass-like clusters of events were generally within the distance of 5km from waterfront,and the linear distribution of the earthquakes could be extended to a distance of 16 kilometers away from waterfront.In Hubei section of Three Gorges Reservoir,earthquakes were mainly concentrated in the northern end of Xiannüfeng and Jiuwanxi Fault in the vicinity of the Xiangxihe river,and along the banks of the Yangtze river at the east of Xietan village and at Shenlongxi area on the northern bank in Badong region;the focal depths were less than 10km,and 4km in average.Earthquake frequency of the reservoir region had a positive correlation with reservoir water level fluctuation,indicating that the seismicity belonged to the reservoir induced earthquakes.Along the Shenlong river in the reservoir area,earthquakes showed three linear distributions in the northern Badong County,which was related to karst distribution.There are underground rivers along carbonate strata.When reservoir was impounded,water permeated into the underground rivers,thus inducing earthquakes.Earthquakes in the areas on the cross-river segment of Xiannüfeng Fault,the Jiuwanxi Fault and at the areas west of Xietan,Shazhen and Xizhen,may be related to the softening of discontinuities,such as the Nukou Fault,the Xiannüfeng Fault or the bedding joints,etc.,which would lead to failure of rock masses,thus,inducing earthquakes.However,convincing conclusions about the triggering mechanism still need further study.In addition,in the areas south of Wenhua and Yanglin of Zigui County and at Rangkou town east of Badong county,there are mining-induced earthquakes at the mines nearby.And on the shores of the reservoir,there are some collapse earthquakes.
引文
①刘远征,2010,长江三峡水库野外实习报告。
车用太,陈俊华,张莉芬,等.2009.长江三峡工程库首区胡家坪4.1水库诱发地震研究[J].地震,29(4):1—13.CHE Yong-tai,CHENJun-hua,ZHANG Li-fen,et al.2009.Study of the reservoir-induced HujiapingMS4.1earthquakein the Three Gorges dam area[J].Earthquake,29(4):1—13(in Chinese).
胡毓良,杨清源.1998.长江三峡工程周边地区的采矿诱发地震[J].地震地质,20(4):349—360.HU Yu-liang,YANG Qing-yuan.1998.Mining-induced earthquakes in the area around the Yangtze Gorge Project[J].Seismology and Geology,20(4):349—360(in Chinese).
马文涛,杨清源,陈献程,等.1996.长江三峡工程区微震的观测与研究[J].地震地质,18(2):161—168.MA Wen-tao,YANG Qing-yuan,CHEN Xian-cheng,et al.1996.Study on microearthquakes in the proposed ThreeGorge reservoir area[J].Seismology and Geology,18(2):161—168(in Chinese).
廖武林,张丽芬,姚运生.2009.三峡水库地震活动特征研究[J].地震地质,31(4):707—714.LIAO Wu-lin,ZHANG Li-fen,YAO Yun-sheng,et al.2009.Characteristics of seismicity in the Three Gorges reservoirarea[J].Seismology and Geology,31(4):707—714(in Chinese).
夏金梧,李长安,曾新平,等.2008.三峡工程库首区高桥断裂特征与地震活动性研究[J].大地测量与地球动力学,28(2):8—15.XIA Jin-wu,LI Chang-an,ZENG Xin-ping,et al.2008.Study on characteristics and seismic activity of Gaoqiao Fault inthe head area of Three Gorges Reservoir[J].Journal of Geodesy and Geodynamics,28(2):8—15(in Chinese).
严尊国,薛军蓉.1987.长江三峡地区弱震重新定位[J].中国地震,3(1):52—59.YAN Zun-guo,XUE Jun-rong.1987.Relocation of weak earthquakes occurring in the Gorge Region of Yangtze River[J].Earthquake Research in China,3(1):52—59(in Chinese).
严尊国.1994.长江三峡及邻近区地震活动性研究[J].地壳形变与地震,l4(2):47—55.YAN Zun-guo.1994.Study on seismicity in the Yangtze Gorges and its vicinity[J].Crustal Deformation and Earth-quake,14(2):47—55(in Chinese).
杨清源,陈献程,马文涛,等.1994.长江三峡地区盐关微地震群的成因机制[J].地震地质,15(3):247—252.YANG Qing-yuan,CHEN Xian-cheng,MA Wen-tao,et al.1994.Formation mechanism of microearthquake swarm inYanguan area on the Yangtze Gorges[J].Seismology and Geology,15(3):247—252(in Chinese).
张爱民,李强.2006.双差定位法在三峡库区地震定位中的应用[J].大地测量与地球动力学,26(3):73—77.ZHANG Ai-min,LI Qiang.2006.Application of double-difference location method to eathquake in Three Gorges Reser-voir area[J].Journal of Geodesy and Geodynamics,26(3):73—77(in Chinese).
张更生等.1959.水文地质工程地质论文集[C].北京:地质出版社.ZHANG Geng-sheng.1959.ACollection of Papers on Hydrogeology and Engineering Geology[C].Geological Publish-ing House,Beijing(in Chinese).
赵旭,李强,蔡晋安,等.2007.三峡库首区最小一维速度模型研究[J].大地测量与地球动力学,27(专刊):1—7.ZHAO Xu,LI Qiang,CAI Jin-an,et al.2007.On minimum1-D velocity model applied in Three Gorges area[J].Journal of Geodesy and Geodynamics,27(Specia1):1—7(in Chinese).
HU Yu-liang,ZHAO Meng,HU Ping,et al.1995.Estimation of potential risk of reservoir-induced earthquake for theproposed hydroelectric project on the Yangtze Gorges[J].Earthquake Research in China,9(4):403—412.
HU Yu-liang,LIU Zu-yuan,YANG Qing-yuan,et al.1996.Induced seismicity at Wujiangdu Reservoir,China:A caseinduced in the karst area[J].Pure and Applied Geophysics,147(2):409—418.
Waldhauser F,Ellsworth W L.2000.A double-difference earthquake location algorithm:Method and application to thenorthern Hayward Fault,California[J].Bulletin of Seismological Society of America,90(6):1353—1368.
车用太,陈俊华,张莉芬,等.2009.长江三峡工程库首区胡家坪4.1水库诱发地震研究[J].地震,29(4):1—13.CHE Yong-tai,CHENJun-hua,ZHANG Li-fen,et al.2009.Study of the reservoir-induced HujiapingMS4.1earthquakein the Three Gorges dam area[J].Earthquake,29(4):1—13(in Chinese).
胡毓良,杨清源.1998.长江三峡工程周边地区的采矿诱发地震[J].地震地质,20(4):349—360.HU Yu-liang,YANG Qing-yuan.1998.Mining-induced earthquakes in the area around the Yangtze Gorge Project[J].Seismology and Geology,20(4):349—360(in Chinese).
马文涛,杨清源,陈献程,等.1996.长江三峡工程区微震的观测与研究[J].地震地质,18(2):161—168.MA Wen-tao,YANG Qing-yuan,CHEN Xian-cheng,et al.1996.Study on microearthquakes in the proposed ThreeGorge reservoir area[J].Seismology and Geology,18(2):161—168(in Chinese).
廖武林,张丽芬,姚运生.2009.三峡水库地震活动特征研究[J].地震地质,31(4):707—714.LIAO Wu-lin,ZHANG Li-fen,YAO Yun-sheng,et al.2009.Characteristics of seismicity in the Three Gorges reservoirarea[J].Seismology and Geology,31(4):707—714(in Chinese).
夏金梧,李长安,曾新平,等.2008.三峡工程库首区高桥断裂特征与地震活动性研究[J].大地测量与地球动力学,28(2):8—15.XIA Jin-wu,LI Chang-an,ZENG Xin-ping,et al.2008.Study on characteristics and seismic activity of Gaoqiao Fault inthe head area of Three Gorges Reservoir[J].Journal of Geodesy and Geodynamics,28(2):8—15(in Chinese).
严尊国,薛军蓉.1987.长江三峡地区弱震重新定位[J].中国地震,3(1):52—59.YAN Zun-guo,XUE Jun-rong.1987.Relocation of weak earthquakes occurring in the Gorge Region of Yangtze River[J].Earthquake Research in China,3(1):52—59(in Chinese).
严尊国.1994.长江三峡及邻近区地震活动性研究[J].地壳形变与地震,l4(2):47—55.YAN Zun-guo.1994.Study on seismicity in the Yangtze Gorges and its vicinity[J].Crustal Deformation and Earth-quake,14(2):47—55(in Chinese).
杨清源,陈献程,马文涛,等.1994.长江三峡地区盐关微地震群的成因机制[J].地震地质,15(3):247—252.YANG Qing-yuan,CHEN Xian-cheng,MA Wen-tao,et al.1994.Formation mechanism of microearthquake swarm inYanguan area on the Yangtze Gorges[J].Seismology and Geology,15(3):247—252(in Chinese).
张爱民,李强.2006.双差定位法在三峡库区地震定位中的应用[J].大地测量与地球动力学,26(3):73—77.ZHANG Ai-min,LI Qiang.2006.Application of double-difference location method to eathquake in Three Gorges Reser-voir area[J].Journal of Geodesy and Geodynamics,26(3):73—77(in Chinese).
张更生等.1959.水文地质工程地质论文集[C].北京:地质出版社.ZHANG Geng-sheng.1959.ACollection of Papers on Hydrogeology and Engineering Geology[C].Geological Publish-ing House,Beijing(in Chinese).
赵旭,李强,蔡晋安,等.2007.三峡库首区最小一维速度模型研究[J].大地测量与地球动力学,27(专刊):1—7.ZHAO Xu,LI Qiang,CAI Jin-an,et al.2007.On minimum1-D velocity model applied in Three Gorges area[J].Journal of Geodesy and Geodynamics,27(Specia1):1—7(in Chinese).
HU Yu-liang,ZHAO Meng,HU Ping,et al.1995.Estimation of potential risk of reservoir-induced earthquake for theproposed hydroelectric project on the Yangtze Gorges[J].Earthquake Research in China,9(4):403—412.
HU Yu-liang,LIU Zu-yuan,YANG Qing-yuan,et al.1996.Induced seismicity at Wujiangdu Reservoir,China:A caseinduced in the karst area[J].Pure and Applied Geophysics,147(2):409—418.
Waldhauser F,Ellsworth W L.2000.A double-difference earthquake location algorithm:Method and application to thenorthern Hayward Fault,California[J].Bulletin of Seismological Society of America,90(6):1353—1368.
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