P波极性数据所揭示的台湾地区三维应力结构的初步结果
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摘要
采用综合震源机制方法,利用503393个P波极性数据反演了台湾地区的三维应力结构.对于给定点,根据该点及邻近区域地震的所有P波极性数据采用地震综合震源机制进行估算,P波极性数据的权重由高斯距离函数给定.该方法可以采用大量P波极性数据,包括不能确定单个地震震源机制的P波极性数据.与传统的震源机制确定应力场的方法相比,该方法可以提供更好的震源机制的平均结果并覆盖更为广泛的地区.本文求得了台湾及邻区0.25°×0.25°×2.5 km的综合震源机制.初步结果表明,P轴和T轴方向在Moho间断面附近变化明显.P轴和T轴方向在15～45 km深度范围内与P波速度异常相关,描绘出菲律宾板块在台湾西北部的北西向俯冲消减.该三维应力场结果可为台湾地区的地球动力学过程提供新的约束.
We apply the composite focal mechanism method and use more than half million P wave polarity data to invert for the 3-D stress field in Taiwan region.At a given location,composite focal mechanism is estimated using all the P wave polarity data originated from its neighborhood, and the data are weighted using a Gaussian distance weighting function.This method has the advantage of allowing maximum amount of data input in the solution,including polarity data from small earthquakes whose focal mechanisms are undeterminable with too few observation data available.Comparing to traditional focal mechanism estimation methods,this method produces focal mechanism estimates covering a broader area,and provides better averages of local focal mechanism solutions.We present the focal mechanism result in a 0.25°×0.25°×2.5 km grid in Taiwan and its adjacent areas.The preliminary result shows that the P and T axis directions change markedly across the Moho discontinuity.The P and T axis directions in the 15～45 km depth range also correlate with P wave velocity perturbations and delineate the northwestward subduction of the Philippine Sea plate in northeast Taiwan.This 3-D stress field result may provide new constraints on geodynamics process in Taiwan region.
We apply the composite focal mechanism method and use more than half million P wave polarity data to invert for the 3-D stress field in Taiwan region.At a given location,composite focal mechanism is estimated using all the P wave polarity data originated from its neighborhood, and the data are weighted using a Gaussian distance weighting function.This method has the advantage of allowing maximum amount of data input in the solution,including polarity data from small earthquakes whose focal mechanisms are undeterminable with too few observation data available.Comparing to traditional focal mechanism estimation methods,this method produces focal mechanism estimates covering a broader area,and provides better averages of local focal mechanism solutions.We present the focal mechanism result in a 0.25°×0.25°×2.5 km grid in Taiwan and its adjacent areas.The preliminary result shows that the P and T axis directions change markedly across the Moho discontinuity.The P and T axis directions in the 15～45 km depth range also correlate with P wave velocity perturbations and delineate the northwestward subduction of the Philippine Sea plate in northeast Taiwan.This 3-D stress field result may provide new constraints on geodynamics process in Taiwan region.
引文
[1]Yu S B,Chen H Y,Kuo L C.Velocity field of GPS stations in the Taiwan area.Tectono physics,1997,274(1-3):41- ??59
[2]Suppe J.Mechanics of mountain building and metamorphism in Taiwan.Mem.Geol.Soc.China,1981,4:67-89
[3]Davis D,Suppe J,Dahlen F A.Mechanics of fold-and-thrust belts and accretionary wedges.J.Geophys.Res.,1983,88 (B2):1153-1172
[4]Wu F T,Rau R J,Salzberg D.Taiwan orogeny:thinskinned or lithospheric collision? Tectonphysics,1997,274 (1-3):191-220
[5]李锡堤.大地应力分析与弧陆碰撞对于台湾北部古应力场变迁之影响[Ph.D.Thesis].台北:国立台湾大学地质研究所,1986.PP202 Li X D.Crustal Stress Analysis and the Effects of Arc-Continent Collision on North Part of Taiwan Region(in Chinese)[Ph.D.Thesis].Taibei:Institute of Geosciences, National Taiwan University,1986.PP202
[6]Yeh Y H,Barrier E,Lin C H,et al.Stress tensor analysis in the Taiwan area from focal mechanisms of earthquakes. Tectonophysics,1991,200(1-3):267-280
[7]Rau R J,Wu F T.Active tectonics of Taiwan orogeny from focal mechanisms of small-to-moderate-sized earthquakes. TAO,1998,9(4):755-778
[8]Wu Y M,Zhao L,Chang C H,et al.Focal mechanism determination in Taiwan by genetic algorithm.Bull.Seism. Soc.Amer.,2008,98(2):651-661
[9]Wu Y M,Chang C H,Zhao L,et al.Seismic tomography of Taiwan:improved constraints from a dense network of strong-motion stations.J.Geophys.Res.,2007,112:B08312, doi:10.1029/2007JB004983
[10]Wu Y M,Chang C H,Zhao L,et al.A comprehensive relocation of earthquakes in Taiwan from 1991 to 2005.Bull. Seism.Soc.Amer.,2008,98(3),1471-1481
[11]Wu Y M,Hsu Y J,Chang C H,et al.Temporal and spatial variation of stress field in Taiwan from 1991 to 2007:Insights from comprehensive first motion focal mechanism catalog. Earth Planet Sci.Lett.,2010,298(3-4):306-316
[12]Gephart J W,Forsyth D W.An improved method for determining the regional stress tensor using earthquake focal mechanism data:application to the San Fernando earthquake sequence.J.Geophys.Res.,1984,89(B11):9305-9320
[13]Michael A J.Determination of stress from slip data:faults and folds.J.Geophys.Res.,1984,89(B13):11517- 11526
[14]Horiuchi S,Russo G,Hasegawa A.Discrimination of fault planes from auxiliary planes based on simultaneous determination of stress tensor and a large number of fault plane solutions. J.Geophys.Res.,1995,100(B5):8327-8338
[15]许忠淮,汪素云,高阿甲等.我国部分早期震源机制解答的重新测定.地震地磁观测与研究,1994,15(5):1-9 Xu Z H,Wang S Y,Gao A J,et al.Redetermination of some early focal mechanism solutions of Chinese earthquakes. Seismological and Geomagnetic Observation and Research(in Chinese),1994,16(4):34-42
[16]万永革,吴忠良,周公威等.中国地震震源机制测定结果的比较.地震地磁观测与研究,2001,22(5):1-15 Wan Y G,Wu Z L,Zhou G W,et al.China seismic mechanism comparison for different determination.Seismolagical and Geomagnetic Observation and Research(in Chinese), 2001,22(5):1-15
[17]Aki K.Earthquake generating stress in Japan for the years 1961 to 1963 obtained by smoothing the first motion radiation patterns.Bull.Earthq.Res.Inst.,1966,44(2):447-471
[18]李钦祖,王泽皋,贾云年等.由单台小地震资料所得两个区域的应力场.地球物理学报,1973,16(1):49-61 Li Q Z,Wang Z G,Jia Y N,et al.Stress field obtained for two regions from weak earthquake data recorded at a single seismic station.Chinese J.Geophys.(Acta Geophysica Sinica) (in Chinese),1973,16(1):49- 61
[19]许忠淮,阎明,赵仲和.由多个小地震推断的华北地区构造应力场的方向.地震学报,1983,5(3):268-279 Xu Z H,Yan M,Zhao Z H.Evaluation of the direction of tectonic stress in North China from recorded data of a large number of small earthquakes.Acta Seismologica Sinica(in Chinese),1983,5(3):268-279
[20]许忠淮,汪素云,黄雨蕊等.由大量地震的资料推断的我国大陆构造应力场.地球物理学报,1989,32(6):636-647 Xu Z H,Wang S Y,Huang Y R,et al.The tectonic stress field of Chinese continent deduced from a great number of earthquakes.Chinese J.Geophys.(Acta Geophysica Sinica) (in Chinese),1989,32(6):636-647
[21]Xu Z H,Wang S Y,Huang Y R,et al.Tectonic stress field of China inferred from a large number of small earthquakes. J.Geophys.Res.,1992,97(B8):11867-11877
[22]Bokelmann G H R,Beroza G C.Depth-dependent earthquake focal mechanism orientation:Evidence for a weak zone in the lower crust.J.Geophys.Res.,2000,105(B9):21683- 21695
[23]Shen Z K,Jackson D D,Ge B X.Crustal deformation across and beyond the Los Angeles basin from geodetic measurements. J.Geophys.Res.,1996,101(B12):27957-27980
[24]Rau R J,Ching K E,Hu J C,et al.Crustal deformation and block kinematics in transition from collision to subduction: global positioning system measurements in northern Taiwan, 1995～2005.J.Geophys.Res.,2008,113:B09404,doi: 10.1029/2007JB005414
[25]Rau R J,Wu F T.Tomographic imaging of lithospheric structures under Taiwan.Earth Planet.Sci.Lett.,1995, 133(3-4):517-532
[26]Ma K F,Wang J H,Zhao D P.Three-dimensional seismic velocity structure of the crust and uppermost mantle beneath Taiwan.J.Phys.Earth,1996,44(2):85-105
[27]Shin T C,Chen Y L.Study on the earthquake location of 3-D velocity structure in the Taiwan area.Meteorol.Bull.,1988, 42:135-169
[28]Kim K H,Chiu J M,Pujol J,et al.Three-dimensional V_p and V_s structural model associated with the active subduction and collision tectonics in the Taiwan region.Geophys.J. Int.,2005,162(1):204-220
[29]Aki K,Richards P G.Quantitative Seismology:Theory and Methods.San Francisco:W H Freeman,Vol 1,1980.1- 932
[30]万永革.“地震静态应力触发”问题的研究[博士论文].北京:中国地震局地球物理研究所,2001 Wan Y G.Research on "Seismic Static Stress Triggering" Problem(in Chinese)[Ph.D.thesis].Beijing:Institute of Geophysics,China Seismological Bureau,2001
[31]万永革.数字信号处理的MATLAB实现.北京:科学出版社,2007.PP326 Wan Y G.Digital Signal Processing Based on MATLAB(in Chinese).Beijing:Science Press,2007.PP326
[32]万永革,盛书中,许雅儒等.不同应力状态和摩擦系数对综合P波辐射花样影响的模拟研究.地球物理学报,2011,54 (4):994-1001 Wan Y G,Sheng S Z,Hsu Y J,et al.Effect of stress ratio and friction coefficient on composite P wave radiation patterns. Chinese Journal of Geophysics(in Chinese),54(4):994-1001
[33]Wessel P,Smith WMF.New,improved version of generic mapping tools released.EOS Trans.,1998,79(4):579
[2]Suppe J.Mechanics of mountain building and metamorphism in Taiwan.Mem.Geol.Soc.China,1981,4:67-89
[3]Davis D,Suppe J,Dahlen F A.Mechanics of fold-and-thrust belts and accretionary wedges.J.Geophys.Res.,1983,88 (B2):1153-1172
[4]Wu F T,Rau R J,Salzberg D.Taiwan orogeny:thinskinned or lithospheric collision? Tectonphysics,1997,274 (1-3):191-220
[5]李锡堤.大地应力分析与弧陆碰撞对于台湾北部古应力场变迁之影响[Ph.D.Thesis].台北:国立台湾大学地质研究所,1986.PP202 Li X D.Crustal Stress Analysis and the Effects of Arc-Continent Collision on North Part of Taiwan Region(in Chinese)[Ph.D.Thesis].Taibei:Institute of Geosciences, National Taiwan University,1986.PP202
[6]Yeh Y H,Barrier E,Lin C H,et al.Stress tensor analysis in the Taiwan area from focal mechanisms of earthquakes. Tectonophysics,1991,200(1-3):267-280
[7]Rau R J,Wu F T.Active tectonics of Taiwan orogeny from focal mechanisms of small-to-moderate-sized earthquakes. TAO,1998,9(4):755-778
[8]Wu Y M,Zhao L,Chang C H,et al.Focal mechanism determination in Taiwan by genetic algorithm.Bull.Seism. Soc.Amer.,2008,98(2):651-661
[9]Wu Y M,Chang C H,Zhao L,et al.Seismic tomography of Taiwan:improved constraints from a dense network of strong-motion stations.J.Geophys.Res.,2007,112:B08312, doi:10.1029/2007JB004983
[10]Wu Y M,Chang C H,Zhao L,et al.A comprehensive relocation of earthquakes in Taiwan from 1991 to 2005.Bull. Seism.Soc.Amer.,2008,98(3),1471-1481
[11]Wu Y M,Hsu Y J,Chang C H,et al.Temporal and spatial variation of stress field in Taiwan from 1991 to 2007:Insights from comprehensive first motion focal mechanism catalog. Earth Planet Sci.Lett.,2010,298(3-4):306-316
[12]Gephart J W,Forsyth D W.An improved method for determining the regional stress tensor using earthquake focal mechanism data:application to the San Fernando earthquake sequence.J.Geophys.Res.,1984,89(B11):9305-9320
[13]Michael A J.Determination of stress from slip data:faults and folds.J.Geophys.Res.,1984,89(B13):11517- 11526
[14]Horiuchi S,Russo G,Hasegawa A.Discrimination of fault planes from auxiliary planes based on simultaneous determination of stress tensor and a large number of fault plane solutions. J.Geophys.Res.,1995,100(B5):8327-8338
[15]许忠淮,汪素云,高阿甲等.我国部分早期震源机制解答的重新测定.地震地磁观测与研究,1994,15(5):1-9 Xu Z H,Wang S Y,Gao A J,et al.Redetermination of some early focal mechanism solutions of Chinese earthquakes. Seismological and Geomagnetic Observation and Research(in Chinese),1994,16(4):34-42
[16]万永革,吴忠良,周公威等.中国地震震源机制测定结果的比较.地震地磁观测与研究,2001,22(5):1-15 Wan Y G,Wu Z L,Zhou G W,et al.China seismic mechanism comparison for different determination.Seismolagical and Geomagnetic Observation and Research(in Chinese), 2001,22(5):1-15
[17]Aki K.Earthquake generating stress in Japan for the years 1961 to 1963 obtained by smoothing the first motion radiation patterns.Bull.Earthq.Res.Inst.,1966,44(2):447-471
[18]李钦祖,王泽皋,贾云年等.由单台小地震资料所得两个区域的应力场.地球物理学报,1973,16(1):49-61 Li Q Z,Wang Z G,Jia Y N,et al.Stress field obtained for two regions from weak earthquake data recorded at a single seismic station.Chinese J.Geophys.(Acta Geophysica Sinica) (in Chinese),1973,16(1):49- 61
[19]许忠淮,阎明,赵仲和.由多个小地震推断的华北地区构造应力场的方向.地震学报,1983,5(3):268-279 Xu Z H,Yan M,Zhao Z H.Evaluation of the direction of tectonic stress in North China from recorded data of a large number of small earthquakes.Acta Seismologica Sinica(in Chinese),1983,5(3):268-279
[20]许忠淮,汪素云,黄雨蕊等.由大量地震的资料推断的我国大陆构造应力场.地球物理学报,1989,32(6):636-647 Xu Z H,Wang S Y,Huang Y R,et al.The tectonic stress field of Chinese continent deduced from a great number of earthquakes.Chinese J.Geophys.(Acta Geophysica Sinica) (in Chinese),1989,32(6):636-647
[21]Xu Z H,Wang S Y,Huang Y R,et al.Tectonic stress field of China inferred from a large number of small earthquakes. J.Geophys.Res.,1992,97(B8):11867-11877
[22]Bokelmann G H R,Beroza G C.Depth-dependent earthquake focal mechanism orientation:Evidence for a weak zone in the lower crust.J.Geophys.Res.,2000,105(B9):21683- 21695
[23]Shen Z K,Jackson D D,Ge B X.Crustal deformation across and beyond the Los Angeles basin from geodetic measurements. J.Geophys.Res.,1996,101(B12):27957-27980
[24]Rau R J,Ching K E,Hu J C,et al.Crustal deformation and block kinematics in transition from collision to subduction: global positioning system measurements in northern Taiwan, 1995～2005.J.Geophys.Res.,2008,113:B09404,doi: 10.1029/2007JB005414
[25]Rau R J,Wu F T.Tomographic imaging of lithospheric structures under Taiwan.Earth Planet.Sci.Lett.,1995, 133(3-4):517-532
[26]Ma K F,Wang J H,Zhao D P.Three-dimensional seismic velocity structure of the crust and uppermost mantle beneath Taiwan.J.Phys.Earth,1996,44(2):85-105
[27]Shin T C,Chen Y L.Study on the earthquake location of 3-D velocity structure in the Taiwan area.Meteorol.Bull.,1988, 42:135-169
[28]Kim K H,Chiu J M,Pujol J,et al.Three-dimensional V_p and V_s structural model associated with the active subduction and collision tectonics in the Taiwan region.Geophys.J. Int.,2005,162(1):204-220
[29]Aki K,Richards P G.Quantitative Seismology:Theory and Methods.San Francisco:W H Freeman,Vol 1,1980.1- 932
[30]万永革.“地震静态应力触发”问题的研究[博士论文].北京:中国地震局地球物理研究所,2001 Wan Y G.Research on "Seismic Static Stress Triggering" Problem(in Chinese)[Ph.D.thesis].Beijing:Institute of Geophysics,China Seismological Bureau,2001
[31]万永革.数字信号处理的MATLAB实现.北京:科学出版社,2007.PP326 Wan Y G.Digital Signal Processing Based on MATLAB(in Chinese).Beijing:Science Press,2007.PP326
[32]万永革,盛书中,许雅儒等.不同应力状态和摩擦系数对综合P波辐射花样影响的模拟研究.地球物理学报,2011,54 (4):994-1001 Wan Y G,Sheng S Z,Hsu Y J,et al.Effect of stress ratio and friction coefficient on composite P wave radiation patterns. Chinese Journal of Geophysics(in Chinese),54(4):994-1001
[33]Wessel P,Smith WMF.New,improved version of generic mapping tools released.EOS Trans.,1998,79(4):579
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