伽师强震群的深部动力学条件
|
摘要
根据天山造山带及其两侧的塔里木盆地和准噶尔盆地的岩石圈二维速度结构、二维密度结构、二维电性结构、壳幔过渡带的详细结构以及大地热流和震源深度的分布,再结合对新疆西北部的蛇绿岩带、高压变质带和岩浆岩分布的综合分析,建立了天山造山带的地球动力学“层间插入消减”模型。该模型认为,塔里木板块的中上地壳在库尔勒断裂附近向天山造山带的中下地壳层间插入;而下地壳连同岩石圈地幔向天山造山带的上地幔俯冲消减。在天山的西段(哈萨克斯坦境内),费尔干纳地块由北向南插入到南天山之下约180km的深处,在其东段(中国境内),塔里木盆地由南向北插入南天山之下。这两个具有不同方向的下降板片的接触部位为费尔干纳走滑断裂。我国的伽师、喀什、乌恰地震区均落在这两个具有不同俯冲方向板块的结合部位附近,有着特殊的深部构造背景。南、北两大板块的双向挤压必定产生强大的应力,在地震区附近,这种应力的积累与释放具有4个显著的特点:(1)板片的俯冲消减速度约高达每年22mm左右;(2)应力的积累与释放速率加快;(3)应力释放较容易;(4)应力释放较为集中。这4个特点可能是伽师地区在较短的时间内连续发生数次强震的构造因素。
Based on the 2D velocity structure, 2D density structure, 2D electrical structure, detailed structure of crust-mantle transitional zone, the distribution of heat flow and focal depths,the distribution of ophiolite suites, high pressure metamorphic belts and the magmatic rock in Northwestern Xinjiang, China, a geodynamic model of lithospheric subduction with intrusion of layers into the crust was established for the Tienshan orogenic belt, Tarim basin and Junggar basin. The main points are that middle and upper crust of the Tarim basin intruded into the lower and the middle crust of the Tienshan orogenic belt and the lower crust and the lithospheric mantle of the Tarim basin subducted into the upper mantle of the Tienshan orogenic belt. In western Tienshan (in Kazakstan), the Fergana block inserted the depth of 180 km beneath South Tienshan southward. Both fallen blocks with opposite directions met in the Fergana strike-slip fault. Located at South Tienshan, the Jiashi, Kashi and Wuqia seismic zones fall actually at a boundary of the two subducting slabs with opposite directions, forming a special deep tectonic setting. A strong stress must be generated under the two-direction compression. The accumulation and release of the stress bear the following features: the relative speed of the two subducting slabs is more than 22 mm/y; the speed of stress accumulation and release are accelerated; the stress can be easily released; and the stress release is concentrated. The features mentioned above may be the deep tectonic conditions for Jiashi strong earthquake swarms.
Based on the 2D velocity structure, 2D density structure, 2D electrical structure, detailed structure of crust-mantle transitional zone, the distribution of heat flow and focal depths,the distribution of ophiolite suites, high pressure metamorphic belts and the magmatic rock in Northwestern Xinjiang, China, a geodynamic model of lithospheric subduction with intrusion of layers into the crust was established for the Tienshan orogenic belt, Tarim basin and Junggar basin. The main points are that middle and upper crust of the Tarim basin intruded into the lower and the middle crust of the Tienshan orogenic belt and the lower crust and the lithospheric mantle of the Tarim basin subducted into the upper mantle of the Tienshan orogenic belt. In western Tienshan (in Kazakstan), the Fergana block inserted the depth of 180 km beneath South Tienshan southward. Both fallen blocks with opposite directions met in the Fergana strike-slip fault. Located at South Tienshan, the Jiashi, Kashi and Wuqia seismic zones fall actually at a boundary of the two subducting slabs with opposite directions, forming a special deep tectonic setting. A strong stress must be generated under the two-direction compression. The accumulation and release of the stress bear the following features: the relative speed of the two subducting slabs is more than 22 mm/y; the speed of stress accumulation and release are accelerated; the stress can be easily released; and the stress release is concentrated. The features mentioned above may be the deep tectonic conditions for Jiashi strong earthquake swarms.
引文
刘国栋.1994.中国大陆岩石圈结构与动力学[J].地球物理学报,37(增刊Ⅱ):65-81.
刘和甫.1994.天山两侧前陆冲断系构造模式与前陆盆地演化[J].地球科学,中国地质大学学报,19(6):727-740.
马宗晋,傅征祥,等.1980.亚欧地震系的地震构造特征[J].中国科学,9:883-890.
肖序常,汤耀庆,李锦轶,等.1992.新疆北部及邻区大地构造[M].北京:地质出版社.1-100.
肖序常,汤耀庆,李锦轶,等.1990.试论新疆北部大地构造演化[A].见:305项目“新疆地质科学”编委会编.新疆地质科学(第1辑)[M].北京:地质出版社.47-52.
赵俊猛.1998.天山造山带与准噶尔盆地岩石圈结构用其动力学过程[D].北京:中国地震局地质研究所.
赵俊猛,刘国栋,卢造勋,等.2001.天山造山带与准噶尔盆地地壳过渡带及其动力学含义[J].中国科学,D辑,31(4):272-282.
Billington S,Isacks B L,Barazangi M.1997.Spatial distribution andfocal mechanisms of mantle earthquakes in the Hindu Kush?Pam-ir region:Acontorted Benioff zone[J].Geology,5(11):699-704.
Burtman VS,Molnar P.1993.Geological and geophysical evidence fordeep subduction of continental crust beneath the Pamir[J].TheGeological Society of America:281.
Chatelain J L,Roecker S W,Hatzfeld D,et al.1980.Microearthquakeseismicity and fault plane solutions in the Hindu Kush region andtheir tectonic implications[J].Journal of Geophysical Research,85(B3):1365-1388.
Gubin I Y.1960.Regularities of seismic phenomena in the Territory ofTadjikstan:Moscow[M],Academi Nauk USSR.464.
Hamburger MW,Sarewitz D R,Pavlis TL,et al.1992.Structure andseismic evidence for intracontinental subduction in the Peter theFirst Range[J].Central Asia:Geological Society of America Bul-letin,104:397-408.
Leith W,Simpson D W.1986.Seismic domains with in the Gissar-Kokshal seismic zone[J].Soviet Central Asia:Journal of Geo-physical Research,91:689-699.
Molnar P,Gipson M.1996.A bound on the rheology of continentallithosphere using very long baseline interferometry:The velocity ofSouthern China with respect to Eurasia[J].J.Geophys.Res.,101:545-554.
Nelson M,McCaffrey R,Molnar P.1987.Source parameters for11earthquakes in the Tienshan,Central Asia,determined by P andSH waveform inversion[J].J.Geophys.Res,92(B12):12629-12648.
Oliver J,Isacks B.1967.Deep Earthquake Zones,Anomalous Struc-tures in the Upper Mantle and the Lithosphere[J].Journal of Ge-ophysical Research,72:4259.
Roecker S W.1982.Velocity structure of the Pamir-Hindu Kush re-gion:Possible evidence of subducted crust[J].Journal of Geo-physical Research,87(B2):945-959.
Tapponnier P,Molnar P.1979.Active faulting and Cenozoic tectonicsof the Tien Shan,Mongolia,and Baykal regions[J].J.Geo-phys.Res.,84:3425-33459.
Roecker S W,Soboleva O V,Nersevov I L.1980.Seismicity and faultplane solutions of intermediate depth earthquakes in the Pamir-Hindu Kush region[J].Journal of Geophysical Research,85(B3):1358-1364.
Vinnik L P,Lukk A A.1973.Velocity inhomogenities in the uppermantle of Central Asia[J].Dokl.Acad.Sci.USSR Earth Sci.Sect.,213,8-11.
Vinnik L P,Lukk A A,Nersesov I L.1977.Nature of the intermedi-ate seismic zone in the mantle of the Pamir-Hindu Kush[J].Tectonophysics,38:9-14.
刘和甫.1994.天山两侧前陆冲断系构造模式与前陆盆地演化[J].地球科学,中国地质大学学报,19(6):727-740.
马宗晋,傅征祥,等.1980.亚欧地震系的地震构造特征[J].中国科学,9:883-890.
肖序常,汤耀庆,李锦轶,等.1992.新疆北部及邻区大地构造[M].北京:地质出版社.1-100.
肖序常,汤耀庆,李锦轶,等.1990.试论新疆北部大地构造演化[A].见:305项目“新疆地质科学”编委会编.新疆地质科学(第1辑)[M].北京:地质出版社.47-52.
赵俊猛.1998.天山造山带与准噶尔盆地岩石圈结构用其动力学过程[D].北京:中国地震局地质研究所.
赵俊猛,刘国栋,卢造勋,等.2001.天山造山带与准噶尔盆地地壳过渡带及其动力学含义[J].中国科学,D辑,31(4):272-282.
Billington S,Isacks B L,Barazangi M.1997.Spatial distribution andfocal mechanisms of mantle earthquakes in the Hindu Kush?Pam-ir region:Acontorted Benioff zone[J].Geology,5(11):699-704.
Burtman VS,Molnar P.1993.Geological and geophysical evidence fordeep subduction of continental crust beneath the Pamir[J].TheGeological Society of America:281.
Chatelain J L,Roecker S W,Hatzfeld D,et al.1980.Microearthquakeseismicity and fault plane solutions in the Hindu Kush region andtheir tectonic implications[J].Journal of Geophysical Research,85(B3):1365-1388.
Gubin I Y.1960.Regularities of seismic phenomena in the Territory ofTadjikstan:Moscow[M],Academi Nauk USSR.464.
Hamburger MW,Sarewitz D R,Pavlis TL,et al.1992.Structure andseismic evidence for intracontinental subduction in the Peter theFirst Range[J].Central Asia:Geological Society of America Bul-letin,104:397-408.
Leith W,Simpson D W.1986.Seismic domains with in the Gissar-Kokshal seismic zone[J].Soviet Central Asia:Journal of Geo-physical Research,91:689-699.
Molnar P,Gipson M.1996.A bound on the rheology of continentallithosphere using very long baseline interferometry:The velocity ofSouthern China with respect to Eurasia[J].J.Geophys.Res.,101:545-554.
Nelson M,McCaffrey R,Molnar P.1987.Source parameters for11earthquakes in the Tienshan,Central Asia,determined by P andSH waveform inversion[J].J.Geophys.Res,92(B12):12629-12648.
Oliver J,Isacks B.1967.Deep Earthquake Zones,Anomalous Struc-tures in the Upper Mantle and the Lithosphere[J].Journal of Ge-ophysical Research,72:4259.
Roecker S W.1982.Velocity structure of the Pamir-Hindu Kush re-gion:Possible evidence of subducted crust[J].Journal of Geo-physical Research,87(B2):945-959.
Tapponnier P,Molnar P.1979.Active faulting and Cenozoic tectonicsof the Tien Shan,Mongolia,and Baykal regions[J].J.Geo-phys.Res.,84:3425-33459.
Roecker S W,Soboleva O V,Nersevov I L.1980.Seismicity and faultplane solutions of intermediate depth earthquakes in the Pamir-Hindu Kush region[J].Journal of Geophysical Research,85(B3):1358-1364.
Vinnik L P,Lukk A A.1973.Velocity inhomogenities in the uppermantle of Central Asia[J].Dokl.Acad.Sci.USSR Earth Sci.Sect.,213,8-11.
Vinnik L P,Lukk A A,Nersesov I L.1977.Nature of the intermedi-ate seismic zone in the mantle of the Pamir-Hindu Kush[J].Tectonophysics,38:9-14.
版权所有：© 2023 中国地质图书馆 中国地质调查局地学文献中心