伽师近场地震资料处理——三维速度成像
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摘要
利用三维速度结构和震源位置的联合反演方法,处理了伽师近场地震资料,得到强震区 2 0km以上深度的速度图像.结果表明:震区地壳内 8km以上速度结构横向非均匀性较强,反映了该区厚达数公里的沉积盖层介质特征;1 2～ 1 8km深度速度成像存在北东和北西的低速异常带,它们相交于极震区下方,反映了区域发震构造特征;沿极震区的东西和南北正交方向以及强震群分布的两侧,地壳结构均有明显差异,这是强震群孕育的构造背景
A joint inversion of 3 D velocity structure and hypocenter positions was used in Jiashi nearfield data processing. Velocity imaging over the depth of 20 km has been obtained. The results show that velocity structure over the depth of 8 km is strongly and horizontally heterogeneous. Characteristics of sedimentary cover of several kilometers in this region is revealed. Velocity imaging at 12～18 km depths shows two low velocity zones, one trending NE and the other NW. They intersect below the meizoseismal area, revealing characteristics of earthquake occurrence tectonics in this region. Obvious difference exist in crust structure along the EW and the SN direction in the meizoseismal area and on the two sides of the strong earthquake sequence zone. This is one of the deep backgrounds of strong earthquakes development.
A joint inversion of 3 D velocity structure and hypocenter positions was used in Jiashi nearfield data processing. Velocity imaging over the depth of 20 km has been obtained. The results show that velocity structure over the depth of 8 km is strongly and horizontally heterogeneous. Characteristics of sedimentary cover of several kilometers in this region is revealed. Velocity imaging at 12～18 km depths shows two low velocity zones, one trending NE and the other NW. They intersect below the meizoseismal area, revealing characteristics of earthquake occurrence tectonics in this region. Obvious difference exist in crust structure along the EW and the SN direction in the meizoseismal area and on the two sides of the strong earthquake sequence zone. This is one of the deep backgrounds of strong earthquakes development.
引文
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[2] 周仕勇,许忠淮,陈晓非.1997年新疆伽师强震群生成机理研究,自然科学进展,2001,11(9):999～1004
[3] 赵翠萍,顾瑾平,白彤霞.新疆伽师强震群震源应力环境分析.中国地震,2001,17(3):289～298
[4] 段永红,赖晓玲,李松林,等.新疆伽师地震的近场观测和对它的初步认识.地球物理学进展,1999,14(4):28～40
[5] 刘启元,陈九辉,李顺成,等.新疆伽师强震群区三维地壳上地幔S波速度结构及其地震成因的探讨.地球物理学报,2000,43(3):356～365
[6] 周仕勇,许忠淮,陈晓非.伽师强震群震源特征及震源机制力学成因分析.地球物理学报,2001,44(5):654～662
[7] 胥 颐,刘福田,刘建华,等.天山地震带的地壳结构与强震构造环境.地球物理学报,2000,43(2):184～193
[8] 赵仲和.多重模型地震定位程序及其在北京台网的应用.地震学报,1983,5(2),242～254
[9] ThurberCH.Earthquakelocationandthree dimensioncrustalstructureintheCoyoteLakearea,centralCalifornia.JGeophysRes,1983,88:8226～8236
[10] PelvisGL,BoolerJR.Themixeddiscrete continuousinverseproblem:Applicationtothesimultaneousdeterminationofearthquakehypocentersandvelocitystructure.JGeophysRes,1980,85:4801～4810
[11] UmJ,ThurberCH.Afastalgorithmfortwo pointseismicraytracing.BullSeismSocAm,1987,77(3):972～986
[12] 胡方秋,胡 军,柏美祥,等.新疆地震构造.见:马杏垣主编.中国岩石圈动力学地图集.北京:中国地图出版社,1989.56～57
[13] 王 琪,丁国瑜,乔学军,等.用GPS研究南天山(伽师)地区现今地壳变形.地震学报,2000,22(3):263～270
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