利用地震走时层析成像方法确定西昌地区断裂带深部几何形态
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摘要
断裂深部产状和空间几何关系是研究地壳运动变形、动力作用及其地表响应的基础,也是模拟发震断裂与强震关系的基础。为了研究川西南地区强震活动与安宁河、则木河和金河断裂的关系,对盐源-西昌-雷波高分辨地震折射剖面初至Pg波走时和断层面反射波走时进行模拟,获得了川滇活动地块东边界带安宁河、则木河和金河断裂的深部形态。结果表明:在上地壳内,安宁河断裂和则木河断裂东倾32°～35°,其速度结构为舌状低速带,二者规模较大,延伸到了基底。金河断裂东倾约30°,向下延伸至少5km。
The geometry of the fault and spatial relations between faults are the basis for studying the crustal deformation,dynamics,their surface response,and for modeling the relations between fault movement and strong earthquake.To fully understand the relation between strong earthquake and deep crustal faults,Anninghe fault,Zemuhe fault and Jinhe fault,we apply the algorithms on seismic ray tracing and travel-time modeling to first arrival Pg wave and reflection wave from the fault for Yanyuan-Xichang-Leibo high-resolution seismic profile,and the direct information on the velocity and fault from three faults mentioned above has been obtained.The results show that:Anninghe fault and Zemuhe fault incline towards east with dip of 32～35 degree,and their velocity structures present low velocity zone of tongue-like shape;those two faults extend downwards to the crystalline basement at large scale and control most strong earthquake activities in this region.Jinhe fault inclines towards east with dip of 30 degree,and extends downwards at least 5 km.
The geometry of the fault and spatial relations between faults are the basis for studying the crustal deformation,dynamics,their surface response,and for modeling the relations between fault movement and strong earthquake.To fully understand the relation between strong earthquake and deep crustal faults,Anninghe fault,Zemuhe fault and Jinhe fault,we apply the algorithms on seismic ray tracing and travel-time modeling to first arrival Pg wave and reflection wave from the fault for Yanyuan-Xichang-Leibo high-resolution seismic profile,and the direct information on the velocity and fault from three faults mentioned above has been obtained.The results show that:Anninghe fault and Zemuhe fault incline towards east with dip of 32～35 degree,and their velocity structures present low velocity zone of tongue-like shape;those two faults extend downwards to the crystalline basement at large scale and control most strong earthquake activities in this region.Jinhe fault inclines towards east with dip of 30 degree,and extends downwards at least 5 km.
引文
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[16]樊计昌,李松林,张先康,等.海原断裂在地壳深处的几何形态及其动力学意义[J].地震学报,2004,26:42-49.Fan JC,Li SL,Zhang XK,et al.Geometrical form of Haiyuan fault zones in the crustal interior and its dynamic meaning[J].Acta Seismologica Sinica,2004,26:42-49.
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[19]Lutter WJ,Fuis GS,Thurber CH,et al.Tomographic images of the upper crust from the Los Angeles basin to the Mojave Desert,California:Results from the Los Angeles Region seismic experiment[J].Journal of Geophysical Research,1999,104(25):543-565.
[2]崔作舟,卢德源,陈纪平,等.攀西地区的深部地壳结构与构造[J].地球物理学报,1987,30(2):566-580.Cui ZZ,Lu DY,Chen JP,et al.The deep crustal structure and tectonic in Panxi region[J].Chinese Journal of Geophysics,1987,30(2):566-580.
[3]熊绍柏,滕吉文,尹周勋,等.攀西构造带南部地壳与上地幔结构的爆炸地震学研究[J].地球物理学报,1986,29(3):235-244.Xiong SB,Teng JW,Yin ZX,et al.The explosion seismology research on the crust and upper mantle structure in the southern Panxi tectonic belt[J].Chinese Journal of Geophysics,1986,29(3):235-244.
[4]尹周勋,熊绍柏.西昌-渡口-牟定地带二维地壳结构的爆炸地震研究[J].地球物理学报,1992,35(4):421-458.Yin ZX,Xiong SB.The explosion seismology research on2-D crustal structure in Xichang-Dukou-Muding regions[J].Chinese Journal of Geophysics,1992,35(4):421-458.
[5]孙克忠,滕吉文,金东敏,等.攀西构造带Q值及其横向不均匀性[J].地球物理学报,1987,30(2):102-104.Sun KZ,Teng JW,Jin DM,et al.Q values for Panxi tectonic belt and lateral heterogeneity[J].Chinese Journal of Geophysics,1987,30(2):102-104.
[6]滕吉文.攀枝花-西昌古裂谷与“活化”的地球物理特征[J].地球物理学报,1987,30(2):581-593.Teng JW.Panzhihua-Xichang ancient rifts and"activation"of geophysical characteristics[J].Chinese Journal of Geophysics,1987,30(2):581-593.
[7]朱介寿.用人工地震初探川西地区的地壳结构[J].成都地质学院学报,1984,3:111-122.Zhu JS.Preliminary study on crustal structure in western Sichuan region with artificial explosion[J].Journal of Chengdu College of Geology,1984,3:111-122.
[8]张先康.从洛杉矶地壳地震实验计划说起[J].国际地震动态,2003,12:8-10.Zhang XK.On crustal seismic experimental program at Los Angeles[J].Recent Developments in World Seismology,2003,12:8-10.
[9]徐朝繁,张先康,刘宝金,等.高分辨折射地震资料处理方法及其应用[J].地球物理学进展,2005,20(4):1052-1058.Xu CF,Zhang XK,Liu BJ,et al.High resolution refraction seismic data processing method and its application[J].Progress in Geophysics,2005,20(4):1052-1058.
[10]王夫运,段永红,杨卓欣,等.川西盐源-马边地震带上地壳速度结构和活动断裂研究—高分辨率地震折射实验结果[J].中国科学(D辑),2008,38(5):611-621.Wang FY,Duan YH,Yang ZX,et al.Upper crustal velocity structure and active fault study along Yanyuan-Mabian seismic belts in the western Sichuan-seismic refraction experimental results with high resolution[J].Science in China(series D),2008,38(5):611-621.
[11]国家地震局西南烈度队.西南地区地震地质及烈度区划探讨[M].北京:地震出版社,1977:1-224.Xinan Intensity Brigade,SSB.Seismogeology and discuss about intensity zoning in the southwest of China[M].Beijing:Seismological Press,1977:1-224.
[12]李坪,杨美娥.第四纪构造活动与活断层[M]//李坪.鲜水河-小江断裂带,北京:地震出版社,1993,22-54.Li P,Yang ME.Quaternary tectonic activity and active fault[M]//Li P.Xiansuihe-Xiaojiang fault zone,Beijing:Seismological Press,1993:22-54.
[13]何宏林,池田安隆.安宁河断裂带晚第四纪运动特征及模式的讨论[J].地震学报,2007,29(5):537-548.He HL,Chitian AL.Faulting on the Anninghe fault zone,Southwest China in late Quaternary and its movement model[J].Acta Seismologica Sinica,2007,29(5):537-548.
[14]黄祖智,唐荣昌.则木河断裂与地震[J].地震研究,1983,6(2):167-177.Huang ZZ,Tang RC.Zemuhe fracture and earthquake[J].Jounal of Seismological Research,1983,6(2):167-177.
[15]程万正.安宁河-则木河-小江带的强震构造环境和运动速率[J].四川地震,2003,2:7-11.Cheng WZ.Tectonic environment of strong earthquake and displacement rates of seismic belts along Anninghe-Zemuhe-Xiaojiag fault zones[J].Earthquake Research in Sichuan,2003,2:7-11.
[16]樊计昌,李松林,张先康,等.海原断裂在地壳深处的几何形态及其动力学意义[J].地震学报,2004,26:42-49.Fan JC,Li SL,Zhang XK,et al.Geometrical form of Haiyuan fault zones in the crustal interior and its dynamic meaning[J].Acta Seismologica Sinica,2004,26:42-49.
[17]Stadtlander R,Brown L.Turning waves and crustal reflection profiling[J].Geophysics,1997,62(1):335-341.
[18]Thurber CH,Roecker SW,Ellsworth WL,et al.Two-dimensional seismic image of the San Andreas fault in the northern Gabilan Range,central California:Evidence for fluids in the fault zone[J].Geophysical Research Letters,1997,24:1591-1594.
[19]Lutter WJ,Fuis GS,Thurber CH,et al.Tomographic images of the upper crust from the Los Angeles basin to the Mojave Desert,California:Results from the Los Angeles Region seismic experiment[J].Journal of Geophysical Research,1999,104(25):543-565.
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