台湾地区地壳形变的弹性块体位错模型
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摘要
在经典的非震形变位错模型中,地壳形变被认为是活动块体刚性运动和上部断层锁定影响的叠加,本文对此模型进行了改进:(1)用活动块体整体运动和内部线性应变、旋转的贡献代替活动块体刚性运动的贡献;(2)用分层介质地壳模型代替半无限介质模型计算断层锁定的影响.利用改进后的非震形变位错模型,拟合了台湾地区1990～1995年间GPS观测资料.结果显示,在东部海岸山脉区,约有30 mm·a~(-1)的汇聚率被奇美断层消耗掉,运动速度从奇美断层向北迅速衰减.在西部平原地区,南部断层是岛内锁定最为强烈的断层,该地区相应的也是史上灾害性地震多发的地区.根据反演结果计算出的应变率与旋转率分布与前人结果在大部分地区一致,主应变率场显示台湾大部分地区存在近NW-SE方向的主压应变,主压应变方向呈扇形分布.旋转率场显示台湾东部和南部地区存在着逆时针旋转率,而西部和北部地区则为顺时针旋转率.
In previous dislocation model,the aseismic crustal deformation is regarded as the sum of the rigid block motion and the effect of the locked fault.We modify the dislocation model in two aspects.Firstly,the block motion is assumed to be the sum of rotation and linear strain rather than the rigid motion.Secondly,the elastic layered-earth model rather than the homogenous half-space model is applied to calculate the effect of the locked part.The 1990～1995 Global Position System (GPS) velocity data of the Taiwan area are used in our dislocation model. Our simulation shows that in eastern Coastal Range,the velocity decreases northward rapidly from Chimei Fault,which may result from the high crustal compressive rate of about 30 mm·a~(-1) at Chimei Fault.In western Taiwan,the most strongly locked faults appear in the southern Coastal Plain where many disaster earthquakes occur frequently.The calculated strain and rotation rates consist with previous results in most areas.The strain rate field reveals the nearly NW SE compression in most parts of Taiwan with a fan-shaped distribution.The rotation rate field reveals anticlockwise rotation in eastern and southern Taiwan while clockwise rotation in western and northern Taiwan,generally.
In previous dislocation model,the aseismic crustal deformation is regarded as the sum of the rigid block motion and the effect of the locked fault.We modify the dislocation model in two aspects.Firstly,the block motion is assumed to be the sum of rotation and linear strain rather than the rigid motion.Secondly,the elastic layered-earth model rather than the homogenous half-space model is applied to calculate the effect of the locked part.The 1990～1995 Global Position System (GPS) velocity data of the Taiwan area are used in our dislocation model. Our simulation shows that in eastern Coastal Range,the velocity decreases northward rapidly from Chimei Fault,which may result from the high crustal compressive rate of about 30 mm·a~(-1) at Chimei Fault.In western Taiwan,the most strongly locked faults appear in the southern Coastal Plain where many disaster earthquakes occur frequently.The calculated strain and rotation rates consist with previous results in most areas.The strain rate field reveals the nearly NW SE compression in most parts of Taiwan with a fan-shaped distribution.The rotation rate field reveals anticlockwise rotation in eastern and southern Taiwan while clockwise rotation in western and northern Taiwan,generally.
引文
[1] Angelier J.Preface.Tectonophysics,1986,t25:Ⅸ～X
[2] Ho C S.A synthesis of the geologic evolution of Taiwan.Tectonophysics,1986,125:1～16
[3] Tsai Y B.Seismotectonics of Taiwan.Tectonophysics,1986, 125:17～37
[4] Vita-Finzi C,Lin J C.Serial reverse and strike slip on imbricate faults:The Coastal Range of east Taiwan.Geology,1998,26:279～281
[5] Fruneau B,Pathier E,Raymond D,et al.Uplift of Tainan Tableland(SW Taiwan)revealed by SAR interferometry. Geophys.Res.Lett.,2001,28:3071～3074
[6] Kao H,Jian P R.Seismogenic patterns in the Taiwan region insights from source parameter inversion of BATS data. Tectonophysics,2001,333:179～198
[7] Huchon P,Barrier E,Bremaecker J C D,et al.Collision and stress trajectories in Taiwan:A finite element model. Tectonophysics,1986,125:179～191
[8] Yeh Y H,Barrier E,Lin C H,et al.Stress tensor analysis in the Taiwan area from focal mechanisms of earthquakes. Tectonophysics,1991,200:267～280
[9] 郑世楠.台湾及其邻近地区大地应力分布的研究[博士论文].台北:国立中央大学地球物理研究所,1995 Cheng S N.The study of stress distribution in and around Taiwan[Ph.D.thesis].Taipei:National Central University,1995
[10] Chang C P,Chang T Y,Angelier J,et al.Strain and stress field in Taiwan oblique convergent system:constraints from GPS observation and tectonic data.Earth Planet.Sci.Lett.,2003,214:115～127
[11] Yu S B,Chen H Y,Kuo L C.Velocity field of GPS stations in the Taiwan area.Tectonophysics,1997,274:41～59
[12] Wang W M,He Y M,Yao Z X.Complexity of the coseismic rupture for 1999 Chi-Chi Earthquake(Taiwan)from inversion of GPS observations.Tectonophysics,2004,382:151～172
[13] Bos A G,Spakman W,Nyst M C J.Surface deformation and tectonic setting of Taiwan inferred from a GPS velocity field.J.Geophys.Res.,2003,108:2458～2475
[14] 何玉梅,姚振兴.中国台湾南部及其周边岛屿现今地壳形变的位错模型.地球物理学报,2002,45:638～645 He Y M,Yao Z X.Dislocation model for current crustal deformation in and around southern Taiwan,China.Chinese J.Geophys.(in Chinese),2002,45:638～645
[15] Yang Y Q,Liu M.Deformation of convergent plates:Evidence from discrepancies between GPS velocities and rigidplate motions.Geophys.Res.Lett.,2002,29:1472～1475
[16] 李延兴,李智,张静华等.中国大陆及周边地区的水平应变场.地球物理学报,2004,47:222～231 Li Y X,Li Z,Zhang J H,et al.Horizontal strain field in Chinese mainland and the surrounding areas.Chinese J.Geophys.(in Chinese),2004,47:222～231
[17] Savage J G.A dislocation model of strain accumulation and release at a subduction zone.J.Geophys.Res.,1983,88:4984～4996
[18] Matsu'ura M,Jackson D D,Cheng A.Dislocation model for aseismic crustal deformation at Hollister.California.J.Geophys.Res.,1986,91:12661～12674
[19] Yu S B,Jackson D D,Yu G K,et al.Dislocation model for crustal deformation in the Longitudinal Valley area,eastern Taiwan.Tectonophysics,1990,183:97～109
[20] 张希,江在森,王双绪等.川滇地区地壳水平运动的弹性块体边界负位错模型与强震地点预测.地震研究,2005,28:119～124 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 Sichuan-Yunnan area.Journal of Seismological Research(in Chinese),2005,28:119～124
[21] 谢小碧,姚振兴.计算分层介质中位错点源静态位移场的广义反射、透射系数矩阵和离散波数方法.地球物理学报,1989,32:270～280 Xie X B,Yao Z X.A generalized reflection-transmission coefficient matrix method to calculate static displacement field of a stratifield half-space by dislocation source.Chinese J.Geophys.(in Chinese),1989,32:270～280
[22] He Y M,Wang W M,Yao Z X.Static deformation due to shear and tensile faults in a layered half-space.Bull.Seismol.Soc.Am.,2003,93:2253～2263
[23] 姚振兴,纪晨.时间域内有限地震断层的反演问题.地球物理学报,1997,40:691～701 Yao Z X,Ji C.The inverse problem of finite fault study in time domain.Chinese J.Geophys.(in Chinese),1997,40:691～701
[24] 姚振兴,张霖斌.波阻抗反演的混合最优化算法.地球物理学进展,1999,14:1～6 Yao Z X,Zhang L B.Hybrid optimization method for acoustic impedance inversion.Progress in Geophysics in Chinese),1999,14:1～6
[25] 郑忠国.随即加权法.应用数学,1987,10:247～253 Zheng Z G.Random weight method.Acta Mathematicae Applicatae Sinica(in Chinese),1987,10:247～253
[26] Okada Y.Internal deformation due to shear and tensile faults in a half-space.Bull.Seismol.Soc.Am.,1992,82:1018～ 1040
[27] Ma K E,Wang J H,Zhao D P.Three-dimensional seismic velocity structure of the crust and uppermost mantle beneath Taiwan.J.Pyhs.Earth,1996,44:85～105
[28] Seno T.The instantaneous rotation vector of the Philippine Sea Plate relative to the Eurasian Plate.Tectonophysics, 1977,42:209～226
[29] Lee J C,Angelier J,Chu H T,et al.Active fault creep variations at Chihshang,Taiwan,revealed by creep meter monitoring,1998～2001． J.Geophys.Rex.,2003,108: 2528～2548
[30] Hsu L,Brgmann R.Surface creep along the Longitudinal Valley fault,Taiwan from InSAR measurements.Geophys. Res.Lett.,2006,33:doi:10． 1029/2005GL024624
[31] Sibuet J C,Letouzey J,Charvet J,et al.Back arc extension in the Okinawa Trough.J.Geophys.Res.,1987,92:14041～ 14063
[32] Viallon C,Huchon P,Barrier E.Opening of the Okinawa basin and collision in Taiwan:a retreating trench model with lateral anchoring.Earth Planet.Sci.Lett.,1986,80:145～155
[33] Lacombe O,Mouthereay F,Angelier J,et al.Structural, geodetic and seismological evidence for tectonic escape in SW Taiwan.Tectonophysics,2001,333:323～345
[34] Lin C H,Yeh Y H,Yen H Y,et al.Three-dimensional elastic wave velocity structure of the Hualien region of Taiwan:Evidence of active crustal exhumation.Tectonics, 1998,17:89～103
[35] Crespi J M,Chan Y C,Swaim M S.Synorogenic extension and exhumation of the Taiwan hinterland.Geology,1996, 24:247～250
[2] Ho C S.A synthesis of the geologic evolution of Taiwan.Tectonophysics,1986,125:1～16
[3] Tsai Y B.Seismotectonics of Taiwan.Tectonophysics,1986, 125:17～37
[4] Vita-Finzi C,Lin J C.Serial reverse and strike slip on imbricate faults:The Coastal Range of east Taiwan.Geology,1998,26:279～281
[5] Fruneau B,Pathier E,Raymond D,et al.Uplift of Tainan Tableland(SW Taiwan)revealed by SAR interferometry. Geophys.Res.Lett.,2001,28:3071～3074
[6] Kao H,Jian P R.Seismogenic patterns in the Taiwan region insights from source parameter inversion of BATS data. Tectonophysics,2001,333:179～198
[7] Huchon P,Barrier E,Bremaecker J C D,et al.Collision and stress trajectories in Taiwan:A finite element model. Tectonophysics,1986,125:179～191
[8] Yeh Y H,Barrier E,Lin C H,et al.Stress tensor analysis in the Taiwan area from focal mechanisms of earthquakes. Tectonophysics,1991,200:267～280
[9] 郑世楠.台湾及其邻近地区大地应力分布的研究[博士论文].台北:国立中央大学地球物理研究所,1995 Cheng S N.The study of stress distribution in and around Taiwan[Ph.D.thesis].Taipei:National Central University,1995
[10] Chang C P,Chang T Y,Angelier J,et al.Strain and stress field in Taiwan oblique convergent system:constraints from GPS observation and tectonic data.Earth Planet.Sci.Lett.,2003,214:115～127
[11] Yu S B,Chen H Y,Kuo L C.Velocity field of GPS stations in the Taiwan area.Tectonophysics,1997,274:41～59
[12] Wang W M,He Y M,Yao Z X.Complexity of the coseismic rupture for 1999 Chi-Chi Earthquake(Taiwan)from inversion of GPS observations.Tectonophysics,2004,382:151～172
[13] Bos A G,Spakman W,Nyst M C J.Surface deformation and tectonic setting of Taiwan inferred from a GPS velocity field.J.Geophys.Res.,2003,108:2458～2475
[14] 何玉梅,姚振兴.中国台湾南部及其周边岛屿现今地壳形变的位错模型.地球物理学报,2002,45:638～645 He Y M,Yao Z X.Dislocation model for current crustal deformation in and around southern Taiwan,China.Chinese J.Geophys.(in Chinese),2002,45:638～645
[15] Yang Y Q,Liu M.Deformation of convergent plates:Evidence from discrepancies between GPS velocities and rigidplate motions.Geophys.Res.Lett.,2002,29:1472～1475
[16] 李延兴,李智,张静华等.中国大陆及周边地区的水平应变场.地球物理学报,2004,47:222～231 Li Y X,Li Z,Zhang J H,et al.Horizontal strain field in Chinese mainland and the surrounding areas.Chinese J.Geophys.(in Chinese),2004,47:222～231
[17] Savage J G.A dislocation model of strain accumulation and release at a subduction zone.J.Geophys.Res.,1983,88:4984～4996
[18] Matsu'ura M,Jackson D D,Cheng A.Dislocation model for aseismic crustal deformation at Hollister.California.J.Geophys.Res.,1986,91:12661～12674
[19] Yu S B,Jackson D D,Yu G K,et al.Dislocation model for crustal deformation in the Longitudinal Valley area,eastern Taiwan.Tectonophysics,1990,183:97～109
[20] 张希,江在森,王双绪等.川滇地区地壳水平运动的弹性块体边界负位错模型与强震地点预测.地震研究,2005,28:119～124 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 Sichuan-Yunnan area.Journal of Seismological Research(in Chinese),2005,28:119～124
[21] 谢小碧,姚振兴.计算分层介质中位错点源静态位移场的广义反射、透射系数矩阵和离散波数方法.地球物理学报,1989,32:270～280 Xie X B,Yao Z X.A generalized reflection-transmission coefficient matrix method to calculate static displacement field of a stratifield half-space by dislocation source.Chinese J.Geophys.(in Chinese),1989,32:270～280
[22] He Y M,Wang W M,Yao Z X.Static deformation due to shear and tensile faults in a layered half-space.Bull.Seismol.Soc.Am.,2003,93:2253～2263
[23] 姚振兴,纪晨.时间域内有限地震断层的反演问题.地球物理学报,1997,40:691～701 Yao Z X,Ji C.The inverse problem of finite fault study in time domain.Chinese J.Geophys.(in Chinese),1997,40:691～701
[24] 姚振兴,张霖斌.波阻抗反演的混合最优化算法.地球物理学进展,1999,14:1～6 Yao Z X,Zhang L B.Hybrid optimization method for acoustic impedance inversion.Progress in Geophysics in Chinese),1999,14:1～6
[25] 郑忠国.随即加权法.应用数学,1987,10:247～253 Zheng Z G.Random weight method.Acta Mathematicae Applicatae Sinica(in Chinese),1987,10:247～253
[26] Okada Y.Internal deformation due to shear and tensile faults in a half-space.Bull.Seismol.Soc.Am.,1992,82:1018～ 1040
[27] Ma K E,Wang J H,Zhao D P.Three-dimensional seismic velocity structure of the crust and uppermost mantle beneath Taiwan.J.Pyhs.Earth,1996,44:85～105
[28] Seno T.The instantaneous rotation vector of the Philippine Sea Plate relative to the Eurasian Plate.Tectonophysics, 1977,42:209～226
[29] Lee J C,Angelier J,Chu H T,et al.Active fault creep variations at Chihshang,Taiwan,revealed by creep meter monitoring,1998～2001． J.Geophys.Rex.,2003,108: 2528～2548
[30] Hsu L,Brgmann R.Surface creep along the Longitudinal Valley fault,Taiwan from InSAR measurements.Geophys. Res.Lett.,2006,33:doi:10． 1029/2005GL024624
[31] Sibuet J C,Letouzey J,Charvet J,et al.Back arc extension in the Okinawa Trough.J.Geophys.Res.,1987,92:14041～ 14063
[32] Viallon C,Huchon P,Barrier E.Opening of the Okinawa basin and collision in Taiwan:a retreating trench model with lateral anchoring.Earth Planet.Sci.Lett.,1986,80:145～155
[33] Lacombe O,Mouthereay F,Angelier J,et al.Structural, geodetic and seismological evidence for tectonic escape in SW Taiwan.Tectonophysics,2001,333:323～345
[34] Lin C H,Yeh Y H,Yen H Y,et al.Three-dimensional elastic wave velocity structure of the Hualien region of Taiwan:Evidence of active crustal exhumation.Tectonics, 1998,17:89～103
[35] Crespi J M,Chan Y C,Swaim M S.Synorogenic extension and exhumation of the Taiwan hinterland.Geology,1996, 24:247～250
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