龙门山及邻区断裂分布及地震前后断裂形态差异
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摘要
利用欧拉方程(欧拉反褶积法)对龙门山地区重力数据进行反演,得到了地震前龙门山及邻区断裂的分布特征及参考深度。汶川地震波及范围广、破坏性大,地震前后发震断裂及周围断裂的形态必然会存在一定差异。笔者布设了一条实测重力剖面来对比地震前后断裂的形态。对比发现,地震后龙门山断裂带的逆冲趋势减弱,映秀—北川断裂与都江堰—江油断裂之间产生了多个破碎带。通过断裂形态的变化探究本次地震的成因,提出了应力面(第二地震面)和多震源的观点。
The fault distributions and reference depths in Longmenshan and adjacent areas before earthquake has been obtained by Euler equation(Euler deconvolution) inversion method about gravity data of Wenchuan area.Wenchuan earthquake spreads widely and causes seriously destructions,which will results in morphology differences in seismogenic fault and peripheral faults.A gravity profile was designed in this area to compare the fault morphology before and after the earthquake.The thrust nature of Longmenshan belt diminished,and a number of fracture zone between Yingxiu-Beichuan fault and Dujiangyan-Jiangyou fault were produced.The viewpoints of stress plane(second earthquake plane) and multi-sources were proposed according to the genesis research about Wenchuan earthquake through fault morphology differences.
The fault distributions and reference depths in Longmenshan and adjacent areas before earthquake has been obtained by Euler equation(Euler deconvolution) inversion method about gravity data of Wenchuan area.Wenchuan earthquake spreads widely and causes seriously destructions,which will results in morphology differences in seismogenic fault and peripheral faults.A gravity profile was designed in this area to compare the fault morphology before and after the earthquake.The thrust nature of Longmenshan belt diminished,and a number of fracture zone between Yingxiu-Beichuan fault and Dujiangyan-Jiangyou fault were produced.The viewpoints of stress plane(second earthquake plane) and multi-sources were proposed according to the genesis research about Wenchuan earthquake through fault morphology differences.
引文
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[2]张培震,徐锡伟,闻学泽,等.2008年汶川8.0级地震发震断裂的滑动速率、复发周期和构造成因[J].地球物理学报,2008,51(4):1066-1073.Zhang Pei-zhen,Xu Xi-wei,Wen Xue-ze,et al.SlipRates and Recurrence Intervals of the Longmen ShanActive Fault Zone,and Tectonic Implication for theMechanism of the May 12 Wenchuan Earthquake,2008,Sichuan,China[J].Chinese Journal ofGeophysics,2008,51(4):1066-1073.
[3]王卫民,赵连锋,李娟,等.四川汶川8.0级地震震源过程[J].地球物理学报,2008,51(5):1403-1410.Wang Wei-min,Zhao Lian-feng,Li Juan,et al.Rupture Process of the Ms8.0 Wenchuan Earthquakeof Sichuan[J].Chinese Journal of Geophysics,2008,51(5):1403-1410.
[4]Thompson D,Euldph T.A New Technique for MakingComputer Assisted Depth Estimates from MagneticData[J].Geophysics,1982,47(1):31-37.
[5]Durrheim R J,Cooper G R J.A Program for the EulerDeconvolution of Magnetic and Gravity Data[J].Com-puters&Geosciences,1998,24(6):545-550.
[6]Cooper G R J.Obtaining Dip and Susceptibility Infor-mation from Euler Deconvolution Using the HoughTransform[J].Computers&Geosciences,2006,32:1592-1599.
[7]Keating P.Weighted Euler Deconvolution of GravityData[J].Geophysics,1998,63(5):1595-1603.
[8]Stavrev P,Reid A.Euler Deconvolution of GravityAnomalies from Thick Contact/Fault Structures withExtended Negative Structural Index[J].Geophysics,2010,75(6):151-158.
[9]Cooper G R J.Euler Deconvolution with ImprovedAccuracy and Multiple Different Structural Indices[J].Journal of China University of Geosciences,2008,19(1):72-76.
[10]四川省地矿局.四川省区域地质志[M].北京:地质出版社,1991:35-121.Bureau of Geology and Mineral Resources of Sichuan.Regional Geology of Sichuan[M].Beijing:Geological Publishing House,1991:35-121.
[11]陈欢欢,李星,丁文秀.Surfer8.0等值线绘制中的十二种插值方法[J].工程地球物理学报,2007,4(1):52-57.Chen Huan-huan,Li Xing,Ding Wen-xiu.Twelve Kinds of Gridding Methods of Surfer8.0in Isoline Drawing[J].Chinese Journal of Engineering Geo-physics,2007,4(1):52-57.
[12]滕吉文,刘财,韩立国,等.汶川—映秀M s 8.0地震的介质破裂与深部物质运移的动力机制[J].吉林大学学报:地球科学版,2009,39(4):549-573.Teng Ji-wen,Liu Cai,Han Li-guo,et al.The Dy-namical Mechanism for Medium Rapture and Motion of Deep Matler on Wenchuan-Yingxiu Ms8.0Earth-quarce,2008[J].Journal of Jilin University:Earth Science Edition,2009,39(4):549-573.
[13]费琪.壳幔物质流变的底辟作用孕育大地震:卫星重力资料的证据[J].地学前缘,2009,16(3):282-293.Fei Qi.Major Earthquakes by Rheological Diapirism of Crust-Mantle Material:Evidence from Satellite Gravity Data[J].Earth Science Frontiers,2009,16(3):282-293.
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