根据断层形变剖面资料分析泾阳口镇-关山断裂活动状况
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摘要
首先分析泾阳地震台1986~2005年跨口镇-关山断层定点形变观测资料,指出形变剖面各点的运动特征:1995年前泾阳台N1A测线资料基本上呈线性变化,1995~1997年该测线形变资料呈现较大的波动性异常,1998年1月5日陕西泾阳发生4.8级地震,靠近断层的点位发生了阶跃式变化,之后各点位运动渐趋于平缓。其后结合断层位错模型引起的地表形变特征,分析得出该形变变化主要由地裂和断裂活动共同引起;不考虑地震引起的异常时段,分析1986~1994以及1999~2005形变年变化量,可看出变化趋势基本一致;最后利用1986~1994形变速率进行断层蠕滑段或地裂速率及深度反演。从反演结果可以看出,基准点N1比较稳定,3号点附近的地裂较浅,底部几十米,以垂直下滑为主,兼有张裂活动;5、6号点之间的断层活动深度在1 km左右。该断层上盘仍在下降。
Data of fixed-point cross fault deformation observation of Jingyang Seismic Station from 1986 to 2005 are analyzed and the movement characteristics of deformation profile are described.The data of survey line NIA at Jingyang station before 1995 basically indicates a linear variation.The deformation data from 1995 to 1997 show great fluctuated anomaly.The Jingyang earthquake of magnitude 4.8 occurred on January 5,1998 in Shaanxi and step changes appeared at the point near the fault.After then,movement at these points becomes stable.Based on analyses of characteristics of surface deformation simulated by fault dislocation model,it is concluded that the deformation changes were caused jointly by activity ground fissures and fault.If not considering abnormal period due to earthquakes,analysis on annual deformation changes from 1986 to 1994 and from 1999 to 2005 show that tendency of changes is basically same.Finally fault creeping segment or ground fissure activity rate and depth are inversed by use of deformation rate from 1986 to 1994.The results of the inversion show that the reference point N1 is relatively stable.Ground rupture near point 3 is relatively shallow with depth about several decameters.Its activity mainly is vertical subsiding with tensional fracture.The faulting depth between point 5 and 6 is about 1 km.The upfaulted block of the fault is still subsiding.
Data of fixed-point cross fault deformation observation of Jingyang Seismic Station from 1986 to 2005 are analyzed and the movement characteristics of deformation profile are described.The data of survey line NIA at Jingyang station before 1995 basically indicates a linear variation.The deformation data from 1995 to 1997 show great fluctuated anomaly.The Jingyang earthquake of magnitude 4.8 occurred on January 5,1998 in Shaanxi and step changes appeared at the point near the fault.After then,movement at these points becomes stable.Based on analyses of characteristics of surface deformation simulated by fault dislocation model,it is concluded that the deformation changes were caused jointly by activity ground fissures and fault.If not considering abnormal period due to earthquakes,analysis on annual deformation changes from 1986 to 1994 and from 1999 to 2005 show that tendency of changes is basically same.Finally fault creeping segment or ground fissure activity rate and depth are inversed by use of deformation rate from 1986 to 1994.The results of the inversion show that the reference point N1 is relatively stable.Ground rupture near point 3 is relatively shallow with depth about several decameters.Its activity mainly is vertical subsiding with tensional fracture.The faulting depth between point 5 and 6 is about 1 km.The upfaulted block of the fault is still subsiding.
引文
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[3]王卫东.陕西地区环境剪应力的分布特征[J].地震地磁观测与研究.2001,22(4):54-58.
[4]戴王强,任隽,赵小茂,等.GPS初步揭示的渭河盆地及其边邻地区地壳水平运动特征[J].地震学报,2004,26(3):256-260.
[5]薛广盈,丁韫玉,袁志祥.渭河断陷盆地地壳速度的层析成像研究[J].地震学报,1997.19(3):283-290.
[6]邢西淳,王争良,毛娟,等.泾阳4.8级地震前后泾阳地震台形变观测资料的异常分析[J].西北地震学报,2000.22(1):98-100.
[7]Okada,Y.Surface deformation due to shear and tensile faults in ahalf-space[J],Bulletin of the Seismological Socirty of America.1985.75(4),pp.1135-1154.
[8]雷英杰,张善文,李继武,等.MATLAB遗传算法工具箱及应用[M].西安:西安电子科技大学出版社,2005.
[9]陈运泰,黄立人,林邦惠,等.用大地测量资料反演的1976年唐山地震的位错模式[J].地球物理学报,1979.22(3):201-216.
[10]王庆良,王文萍,梁伟锋,等.大同机车厂地裂缝强活动深度段位错模型反演[J].地壳形变与地震,1998,18(3):80-84.
[11]赵明,陈运泰,巩守文,等.用水准测量资料反演1990年青海共和地震的震源机制[J].地壳形变与地震,1992,12(4):1-11.
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