川西地区壳幔结构与汶川M_s8.0级地震的孕震背景
|
摘要
收集了四川数字地震台网记录的57个远震事件,并从宽频带数字化三分量地震记录中计算出了马尔康(MEK)、都江堰(YZP)、GP江(JJS)、江油(ZJG)、广元(YTS)、康定(GDS)、汉源(XJP)、雅安(MDS)、峨眉山(EMS)、沐川(WMP)、仁寿(YGD)、荣县(HMS)等12个台站下方的远震P波径向接收函数.另外,引入地震勘探中的动校正技术,将各台的接收函数校正到67°的参考震中距处,然后对接收函数进行叠加以增强信号,并把叠加接收函数作为台站下方的平均接收函数.最后,利用台站下的平均接收函数反演得到S波速度结构.反演结果表明:以锦屏山—龙门山断裂为界,其西侧地壳厚达70 km,而东侧仅为50 km左右Moho面在断裂下方形成了一个陡坎;川西地区的地壳速度结构与川中地区差异较大,主要表现在川西地区的中地壳存在厚度为8-22 km的低速层.在都江堰、雅安一带,低速层的厚度最大,其厚度在20-22 km之间,其上地壳为一个坚硬固体,在区域构造应力场作用下,形成了孕育大地震的构造环境.
In the paper, R-component receiver functions of P-wave under 12 stations in Sichuan (MEK,YZP,JJS,ZJG,YTS,GDS,XJP,MDS,EMS,WMP,YGD,HMS) were calculated from 3- component broad-band digital recording data of 57 distant earthquakes. Additionally, the moveout correction technique in exploration seismology was introduced to correct the receiver functions to the 67° reference epicentral distance. Then the receiver functions were stacked to punctuate signals, and the stacked functions were used as the mean receiver functions under stations. Finally, the mean receiver functions were used to invert for the S-wave velocity structures under stations. Results showed that the depth of Moho in the west of the JinpingshanLongmenshan fault is as thick as 70 km, but only 50 km in the east, indicative of a sharp discontinuity. The crustal velocity structure in the western Sichuan is different from the structure in the middle of Sichuan, in that a low-velocity layer of 8-22 km exists in the middle-crustal beneath the western Sichuan. The thickness of the low-velocity layer is the largest in the region of Dujiangyan and Ya an, between 20 km and 22 km. The upper crustal in this region behaves as a firm solid, forming the seismogenic background under the action of the regional tectonic stress field.
In the paper, R-component receiver functions of P-wave under 12 stations in Sichuan (MEK,YZP,JJS,ZJG,YTS,GDS,XJP,MDS,EMS,WMP,YGD,HMS) were calculated from 3- component broad-band digital recording data of 57 distant earthquakes. Additionally, the moveout correction technique in exploration seismology was introduced to correct the receiver functions to the 67° reference epicentral distance. Then the receiver functions were stacked to punctuate signals, and the stacked functions were used as the mean receiver functions under stations. Finally, the mean receiver functions were used to invert for the S-wave velocity structures under stations. Results showed that the depth of Moho in the west of the JinpingshanLongmenshan fault is as thick as 70 km, but only 50 km in the east, indicative of a sharp discontinuity. The crustal velocity structure in the western Sichuan is different from the structure in the middle of Sichuan, in that a low-velocity layer of 8-22 km exists in the middle-crustal beneath the western Sichuan. The thickness of the low-velocity layer is the largest in the region of Dujiangyan and Ya an, between 20 km and 22 km. The upper crustal in this region behaves as a firm solid, forming the seismogenic background under the action of the regional tectonic stress field.
引文
[1] 程万正,刁桂苓,吕弋培等.川滇地块的震源力学机制、运动速率和活动方式.地震地质,2003,25(1) :71-87 Cheng W Z, Diao G L, Lii Y P, et al. Focal mechanisms, displacement rate and mode of motion of the Sichuan-Yunnan block. Seismology and Geology (in Chinese), 2003,25(1) :71-87
[2] Molnar P, Tapponnier P. Cenozoic tectonics of Asia: effects of a continental collision. Science, 1975,189:419-426
[3] Tapponnier P, Molnar P. Slip-line field theory and large scale continental tectonics. Nature, 264:319
[4] Tapponnier P, Molnar P. Active faulting and tectonics of China. J. Geophys. Res. , 1977, 82(20) :2905-2930
[5] 阚荣举,张四昌,晏枫桐等.我国西南地区现代构造应力场与现代构造活动特征的探讨.地球物理学报,1977,20(2) :96-100 Kan R J, Zhang S C, Yan F T, et al. Present tectonic stress field and its relation to the characteristics of recent tectonic activity in southwestern China. Acta Geophysica Sinica (in Chinese), 1977,20(2) :96-100
[6] 曾融生,孙卫国.青藏高原及其邻区的地震活动性和震源机制及高原物质东流的讨论.地震学报,1992,14(增刊):534-564 Zeng R S, Sun W G. Seismicity and focal mechanism in the Tibetan plateau and its implications to lithospheric flow. Acta Seismologica Sinica (in Chinese) , 1992, 14(Suppl.): 534-564
[7] 张中杰,滕吉文,李英康等.藏南地壳结构与地壳物质东西向“逃逸”.中国科学(D辑),2002,32(10) :793-798 Zhang Z J, Teng J, Li Y K, et al. Crustal structure of seismic velocity in the southern Tibet and east-westward escape of the crustal material. Science in China (Ser. D),2002,32(10) :793-798
[8] Langslon C A. Structure under Mount Rainer, Washington, inferred from teleseismic body waves. J. Geophys. Res. , 1979,84(B9) :4749-4762
[9] Owens T J, Zandat G, Taylor S R. Seismic evidence for an ancient rift beneath the Cumberland Plateau. Tennessee: A detailed analysis of broadband teleseismic P waveforms. J. Geophys. Res. , 1984, 89(B9) :7783-7795
[10] Owens T J, Taylor S R, Zandt G. Crustal structure at regional seismic test network stations determined from inversion of broadband teleseismic P waveforms. Bull. Seism. Soc. Am. ,1987,77:631-632
[11] Ammon C J, Randall G E, Zandt G. On the non-uniqueness of receiver function inversions. J. Geophys. Res. , 1990,95 (B10) : 15303-15318
[12] Randall G E. Efficient calculation of differential seismograms for lithospheric receiver functions. Geophys. J. Int. , 1989,99:469-481
[13] Shaw P R, Orcutt J A. Waveform inversion of seismic refraction data and application to young Pacific crust. Geophys. J. R. Astro. Soc., 1985,82:385-414
[14] 陈炳尉,王恺元,刘万熹等.怒江-澜沧江-金沙江地区大地构造.北京:地质出版社,1987 Chen B W, Wang K Y, Liu W X, et al. Geotectonics in Nujiang-Langcangjiang-Jinshajiang Region. Beijing: Geological Publishing House,1987
[15] Yuan X, Ni J, Kind R, Mechie J, Sandvol E. Lithospheric and upper mantle structure of southern Tibet from a seismological passive source experiment. J. Geophys. Res. ,1997, 102(B12) :27491-27500
[16] Zandt G, Stephen C, Terry C W. Crust and mantle structure across Basin and Range-Colorado Plateau boundary at 37° N latitude and implications for Cenozoic extensional mechanism.J. Geophys. Res., 1995,100(B6) :10529-10548
[17] 王椿镛,楼海,吕智勇等.青藏高原东部地壳上地幔S波速度结构-下地壳流的深部环境.中国科学(D辑),2008,38(1) :22-32 Wang C Y, Lou H, L Z Y, et al. S-wave crustal and upper mantle' s velocity structure in the eastern Tibetan Plateau-Deep environment of lower crustal flow. Science in China (Series D), 2008,51(2) :249-262
[18] Zhu L, Kanamori H. Moho depth variation in southern California from teleseismic receiver function.J. Geophys. Res. , 2000,105(B2) :2969-2980
[19] 张希,江在森,王双绪等.川滇地区地壳水平运动的弹性边界负位错模型与强震地点的预测.地震研究,2005,28(2) :119-124 Zhang X, Jiang Z S, Wang S X, et al. Negative dislocation model of elastic block boundary of horizontal crustal movement and the prediction of strong earthquake position in Sichun-Yunan area. J. Seismological Res. (in Chinese), 2005,28(2) :119-124
[20] 王椿镛,吴建平,楼海等.川西藏东地区的地壳P波速度结构.中国科学(D辑),2003,33(增刊):181-189 Wang C Y, Wu J P, Lou H, et al. Crustal structure for P wave velocity in eastern margin of Tibet plateau. Science in China (Ser. D) (in Chinese) , 2003,33(Suppl.): 181-189
[21] 王椿镛,韩渭宾,吴建平等.松潘-甘孜造山带地壳速度结构.地震学报,2003,25(3) :229-241 Wang C Y, Han W B, Wu J P, et al. Crustal structure beneath the Songpan-Garze orogenic belt. Ada Seismologica Sinica (in Chinese), 2003,25(3) :229-241
[22] 王椿镛,Mooney W D,王溪莉等.川滇地区地壳上地幔三维速度结构研究.地震学报,2002,24(1) :1-16 Wang C Y, Mooney W D, Wang X L, et al. Study on 3-D velocity structure of crust and upper mantle in Sichuan-Yunnan region, China. Acta Seismologica Sinica (in Chinese), 2002,24(1) : 1-16
[23] 毛燕,徐彦,王彬等.四川及邻区Lg尾波的Q值分布特征.地震研究,2005,28(1) :38-42 Mao Y, Xu Y, Wang B, et al. Distribution characteristics of the value Q of Lg coda in Sichuan and its adjacent regions. Journal of Seismological Research (in Chinese), 2005,28(1) :38-42
[2] Molnar P, Tapponnier P. Cenozoic tectonics of Asia: effects of a continental collision. Science, 1975,189:419-426
[3] Tapponnier P, Molnar P. Slip-line field theory and large scale continental tectonics. Nature, 264:319
[4] Tapponnier P, Molnar P. Active faulting and tectonics of China. J. Geophys. Res. , 1977, 82(20) :2905-2930
[5] 阚荣举,张四昌,晏枫桐等.我国西南地区现代构造应力场与现代构造活动特征的探讨.地球物理学报,1977,20(2) :96-100 Kan R J, Zhang S C, Yan F T, et al. Present tectonic stress field and its relation to the characteristics of recent tectonic activity in southwestern China. Acta Geophysica Sinica (in Chinese), 1977,20(2) :96-100
[6] 曾融生,孙卫国.青藏高原及其邻区的地震活动性和震源机制及高原物质东流的讨论.地震学报,1992,14(增刊):534-564 Zeng R S, Sun W G. Seismicity and focal mechanism in the Tibetan plateau and its implications to lithospheric flow. Acta Seismologica Sinica (in Chinese) , 1992, 14(Suppl.): 534-564
[7] 张中杰,滕吉文,李英康等.藏南地壳结构与地壳物质东西向“逃逸”.中国科学(D辑),2002,32(10) :793-798 Zhang Z J, Teng J, Li Y K, et al. Crustal structure of seismic velocity in the southern Tibet and east-westward escape of the crustal material. Science in China (Ser. D),2002,32(10) :793-798
[8] Langslon C A. Structure under Mount Rainer, Washington, inferred from teleseismic body waves. J. Geophys. Res. , 1979,84(B9) :4749-4762
[9] Owens T J, Zandat G, Taylor S R. Seismic evidence for an ancient rift beneath the Cumberland Plateau. Tennessee: A detailed analysis of broadband teleseismic P waveforms. J. Geophys. Res. , 1984, 89(B9) :7783-7795
[10] Owens T J, Taylor S R, Zandt G. Crustal structure at regional seismic test network stations determined from inversion of broadband teleseismic P waveforms. Bull. Seism. Soc. Am. ,1987,77:631-632
[11] Ammon C J, Randall G E, Zandt G. On the non-uniqueness of receiver function inversions. J. Geophys. Res. , 1990,95 (B10) : 15303-15318
[12] Randall G E. Efficient calculation of differential seismograms for lithospheric receiver functions. Geophys. J. Int. , 1989,99:469-481
[13] Shaw P R, Orcutt J A. Waveform inversion of seismic refraction data and application to young Pacific crust. Geophys. J. R. Astro. Soc., 1985,82:385-414
[14] 陈炳尉,王恺元,刘万熹等.怒江-澜沧江-金沙江地区大地构造.北京:地质出版社,1987 Chen B W, Wang K Y, Liu W X, et al. Geotectonics in Nujiang-Langcangjiang-Jinshajiang Region. Beijing: Geological Publishing House,1987
[15] Yuan X, Ni J, Kind R, Mechie J, Sandvol E. Lithospheric and upper mantle structure of southern Tibet from a seismological passive source experiment. J. Geophys. Res. ,1997, 102(B12) :27491-27500
[16] Zandt G, Stephen C, Terry C W. Crust and mantle structure across Basin and Range-Colorado Plateau boundary at 37° N latitude and implications for Cenozoic extensional mechanism.J. Geophys. Res., 1995,100(B6) :10529-10548
[17] 王椿镛,楼海,吕智勇等.青藏高原东部地壳上地幔S波速度结构-下地壳流的深部环境.中国科学(D辑),2008,38(1) :22-32 Wang C Y, Lou H, L Z Y, et al. S-wave crustal and upper mantle' s velocity structure in the eastern Tibetan Plateau-Deep environment of lower crustal flow. Science in China (Series D), 2008,51(2) :249-262
[18] Zhu L, Kanamori H. Moho depth variation in southern California from teleseismic receiver function.J. Geophys. Res. , 2000,105(B2) :2969-2980
[19] 张希,江在森,王双绪等.川滇地区地壳水平运动的弹性边界负位错模型与强震地点的预测.地震研究,2005,28(2) :119-124 Zhang X, Jiang Z S, Wang S X, et al. Negative dislocation model of elastic block boundary of horizontal crustal movement and the prediction of strong earthquake position in Sichun-Yunan area. J. Seismological Res. (in Chinese), 2005,28(2) :119-124
[20] 王椿镛,吴建平,楼海等.川西藏东地区的地壳P波速度结构.中国科学(D辑),2003,33(增刊):181-189 Wang C Y, Wu J P, Lou H, et al. Crustal structure for P wave velocity in eastern margin of Tibet plateau. Science in China (Ser. D) (in Chinese) , 2003,33(Suppl.): 181-189
[21] 王椿镛,韩渭宾,吴建平等.松潘-甘孜造山带地壳速度结构.地震学报,2003,25(3) :229-241 Wang C Y, Han W B, Wu J P, et al. Crustal structure beneath the Songpan-Garze orogenic belt. Ada Seismologica Sinica (in Chinese), 2003,25(3) :229-241
[22] 王椿镛,Mooney W D,王溪莉等.川滇地区地壳上地幔三维速度结构研究.地震学报,2002,24(1) :1-16 Wang C Y, Mooney W D, Wang X L, et al. Study on 3-D velocity structure of crust and upper mantle in Sichuan-Yunnan region, China. Acta Seismologica Sinica (in Chinese), 2002,24(1) : 1-16
[23] 毛燕,徐彦,王彬等.四川及邻区Lg尾波的Q值分布特征.地震研究,2005,28(1) :38-42 Mao Y, Xu Y, Wang B, et al. Distribution characteristics of the value Q of Lg coda in Sichuan and its adjacent regions. Journal of Seismological Research (in Chinese), 2005,28(1) :38-42
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