根据走滑大地震前后应力轴偏转和应力降求取偏应力量值的研究
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摘要
运用走滑地震造成的地震前后应力方向偏转和地震应力降Δτ推导得到地震震源处偏应力量值τ的解析表达式为τ=[Δτcos2(φP′-E)]/sin2(φP′-φP)(其中,φP和φP′分别为地震前后的统计P轴走向,E为地震断层走向.).当震前P轴与震后P轴与断层走向夹角为45°时,该公式失效.对偏应力值与应力降比值随应力场主压应力轴与断层走向夹角及应力场主压应力轴偏转的变化进行分析表明,相同应力降造成的应力轴偏转越大,地下偏应力越小;断层走向越接近主压应力轴方向,地震应力降场对偏应力场的贡献越小.将该方法运用于Landers地震震源区,求得了该地震Homestead Valley段的偏应力量值为10MPa.
In order to get deviatoric stress level τ,the analytic formula is derived according to rotation of stress filed before and after strike-slip type earthquake and the stress drop Δτ of the earthquake as follows:τ=\P--E)]/sin2(φ′-P-φ-P)(φ-P and φ′-P are statistical strikes of P axis before and after earthquake,-E is the strike of seismic fault.). The formula is invalid when the angle of preseismic P axis or postseismic P axis and strike of seismic fault is 45°.It is analyzed that the ratio of deviatoric stress level and stress drop of earthquake changes according to the strike angle of seismic fault and principal pressure axes of deviatoric stress field and rotation angle of principal pressure axes.We found that:(1) the larger of the stress filed rotation caused by the same stress drop,the smaller the deviatoric stress level;(2) the more approach of the fault strike to the principal pressure axes before the earthquake,the less contribution to the deviatoric stress level by the stress drop field.The importance of the formula is discussed.This method is applied in Homestead valley patch of Landers earthquake,the deviatoric stress level is estimated as 10MPa.
In order to get deviatoric stress level τ,the analytic formula is derived according to rotation of stress filed before and after strike-slip type earthquake and the stress drop Δτ of the earthquake as follows:τ=\P--E)]/sin2(φ′-P-φ-P)(φ-P and φ′-P are statistical strikes of P axis before and after earthquake,-E is the strike of seismic fault.). The formula is invalid when the angle of preseismic P axis or postseismic P axis and strike of seismic fault is 45°.It is analyzed that the ratio of deviatoric stress level and stress drop of earthquake changes according to the strike angle of seismic fault and principal pressure axes of deviatoric stress field and rotation angle of principal pressure axes.We found that:(1) the larger of the stress filed rotation caused by the same stress drop,the smaller the deviatoric stress level;(2) the more approach of the fault strike to the principal pressure axes before the earthquake,the less contribution to the deviatoric stress level by the stress drop field.The importance of the formula is discussed.This method is applied in Homestead valley patch of Landers earthquake,the deviatoric stress level is estimated as 10MPa.
引文
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[2]崔效锋,谢富仁.利用震源机制解对中国西南及邻区进行应力分区的初步研究.地震学报,1999,23(5):513~522Cui X F,Xie F R.Preliminary research to determine stress districtsfrom focal mechanism solutions in Southwest China and its adjacentarea.Acta Seismologica Sinica(in Chinese),1999,12(5):562~572
[3]谢富仁,张世民,窦素芹等.青藏高原北、东边缘第四纪构造应力场演化特征.地震学报,1999,23(5):513~522Xie F R,Zhang S M,Dong S Q,et al.Evolution characteristics ofQuaternary tectonics stress field in the north and east margin ofQinghai_Xizang Plateau,Acta Seismologica Sinica(in Chinese),1999,12(5):550~561
[4]许忠淮.东亚地区现今构造应力图的编制.地震学报,2001,23(5):492~501Xu Z H.A present_day tectonic stress field map for Eastern Asiaregion.Acta Seismologica Sicina(in Chinese),2001,14(5):524~533
[5]谢富仁,崔效锋,张景发等.中国现代构造应力场基本特征及分区.见:中国大陆地壳应力环境研究.北京:地质出版社,2003.39~48Xie F R,Cui X F,Zhang J F,et al.The characteristics and stressdistricts of recent tectonics stress field in China.In:Research onRecent Stress in China(in Chinese).Beijing:Geological PublishingHouse,2003.39~48
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[8]赵建涛,崔效锋,谢富仁.唐山地震震源区构造应力场强度的初步分析.地震学报,2002,24(3):268~276Zhao J T,Cui X F,Xie F R.Preliminary analysis of the tectonicstress intensity in the source region of Tangshan earthquake.ActaSeismologica Sinica(in Chinese),2002,15(3):285~293
[9]Spudich P.On the inference of absolute stress levels from seismicradiation.Tectonophysics,1992,211:99~106
[10]Spudich P,Guatteri M,Otsuki K,et al.Use of fault striations anddislocation models to infer tectonic shear stress during the 1995 Hyogo-ken Nanbu(Kobe)earthquake.Bull.Seism.Amer.Soc.,1998,88(2):413~427
[11]Starr A T.Slip in a crystal and rupture in a solid due to shear.Proc.Camb.Phiol.Soc.,1928,24:480~500
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[14]Choy G L,Boatwright J L.Global patterns of radiated seismic energyand apparent stress.J.Geophys.Res.,1995,100:18205~18228
[15]吴忠良,黄静,林碧苍.中国西部地震视应力的空间分布.地震学报,2002,24(3):293~301Wu Z L,Huang J,Lin B C.Distribution of apparent stress inwestern China.Acta Seismologica Sinica(in Chinese),2002,15(3):309~317
[16]McGarr A.On relating apparent stress to the stress causingearthquake fault slip.J.Geophys.Res.,1999,104:3003~3011
[17]陈培善,谷继成,李文香.从断裂力学观点研究地震的破裂过程和地震预报.地球物理学报,1977,20(3):185~202Chen P S,Gu J C,Li W X.A study of the earthquake ruptureprocess and earthquake prediction in the light of fracture mechanics.Chinese J.Geophys.(Acta Geophysica Sinica)(in Chinese),1977,20(3):185~202
[18]陈培善.分析地震波估算地壳内的应力值.地震学报,1981,3(3):251~263Chen P S.An estimation of crustal stress value from analysis ofseismic waves.Acta Seismologica Sinica(in Chinese),1981,3(3):251~263
[19]陈培善,白彤霞,肖磊.根据环境应力场寻找中国大陆地区的潜在地震危险性.地震学报,1995,17(3):294~304Chen P S,Bai T X,Xiao L.In search of potential earthquake sourceregions in the Chinese mainland in the light of ambient shear stressfield.Acta Seismologica Sinica(in Chinese),1995,8(3):365~377
[20]Wyss M,Gillard D,Liang B.An estimate of the absolute stresstensor in Kaoiki,Hawaii.J.Geophys.Res.,1992,97:4763~4768
[21]Aki K,Richards P G.Quantitative seismology:Theory and methods.Vol 1&2,W H Freeman,San Francisco,1980,932
[22]Hauksson E.Crustal structure and seismicity distribution adjacent tothe Pacific and North America plate boundary in Southern California.J.Geophys.Res.,2000,105:13875~13903
[23]Wald D J,Heaton T H.Spatial and temporal distribution of slip forthe 1992 Landers,California earthquake.Bull.Seism.Soc.Amer.,1994,84:668~691
[24]Gephart J W,Forsyth D W.An improved method for determining theregional stress tensor using earthquake focal mechanism data:Application to the San Fernando earthquake sequence.J.Geophys.Res.,1984,89:9305~9320
[25]Gephart J W.FMSI:A FORTRAN program for inverting fault/slickenside and earthquake focal mechanism data to obtain theregional stress tensor.Computer&Geosciences,1990,16:953~989
[26]Hardebeck J L,Hauksson E.Crustal stress field in southernCalifornia and its implications for fault mechanics.J.Geophys.Res.,2001,106:21859~21882
[27]King G C P,Stein R S,Lin J.Static stress changes and thetriggering of earthquakes.Bull.Seism.Soc.Amer.,1994,84:935~953
[28]Troise C,De Natale G,Pingue F,et al.Evidence for static stressinteraction among earthquakes in south_central Apennines(Italy).Geophys.J.Int.,1998,134:809~817
[29]王凯英,马瑾,顾国华等.1996年川滇地区发生的一次应力转向事件.地学前缘,2003,10(S1):233~239Wang K Y,Ma J,Gu G H,et al.Rotation of stress axis in Sichuan_Yunnan region in 1996.Earth Science Frontiers(in Chinese),2003,10(S1):233~239
[2]崔效锋,谢富仁.利用震源机制解对中国西南及邻区进行应力分区的初步研究.地震学报,1999,23(5):513~522Cui X F,Xie F R.Preliminary research to determine stress districtsfrom focal mechanism solutions in Southwest China and its adjacentarea.Acta Seismologica Sinica(in Chinese),1999,12(5):562~572
[3]谢富仁,张世民,窦素芹等.青藏高原北、东边缘第四纪构造应力场演化特征.地震学报,1999,23(5):513~522Xie F R,Zhang S M,Dong S Q,et al.Evolution characteristics ofQuaternary tectonics stress field in the north and east margin ofQinghai_Xizang Plateau,Acta Seismologica Sinica(in Chinese),1999,12(5):550~561
[4]许忠淮.东亚地区现今构造应力图的编制.地震学报,2001,23(5):492~501Xu Z H.A present_day tectonic stress field map for Eastern Asiaregion.Acta Seismologica Sicina(in Chinese),2001,14(5):524~533
[5]谢富仁,崔效锋,张景发等.中国现代构造应力场基本特征及分区.见:中国大陆地壳应力环境研究.北京:地质出版社,2003.39~48Xie F R,Cui X F,Zhang J F,et al.The characteristics and stressdistricts of recent tectonics stress field in China.In:Research onRecent Stress in China(in Chinese).Beijing:Geological PublishingHouse,2003.39~48
[6]谢富仁,李宏.利用断层滑动资料确定鲜水河断裂带构造应力方向和大小.地震学报,1995,17(2):164~171Xie F R,Li H.Determination of the direction and magnitude ofrecent tectonic stress in the Xianshuihe fault zone using fault slipdata.Acta Seismologica Sinica(in Chinese),1995,8(2):205~213
[7]Plenefisch T,Bonjer K P.The stress field in the Rhine Graben areainferred from earthquake focal mechanisms and estimation of frictionalparameters.Tectonophysics,1997,275:71~97
[8]赵建涛,崔效锋,谢富仁.唐山地震震源区构造应力场强度的初步分析.地震学报,2002,24(3):268~276Zhao J T,Cui X F,Xie F R.Preliminary analysis of the tectonicstress intensity in the source region of Tangshan earthquake.ActaSeismologica Sinica(in Chinese),2002,15(3):285~293
[9]Spudich P.On the inference of absolute stress levels from seismicradiation.Tectonophysics,1992,211:99~106
[10]Spudich P,Guatteri M,Otsuki K,et al.Use of fault striations anddislocation models to infer tectonic shear stress during the 1995 Hyogo-ken Nanbu(Kobe)earthquake.Bull.Seism.Amer.Soc.,1998,88(2):413~427
[11]Starr A T.Slip in a crystal and rupture in a solid due to shear.Proc.Camb.Phiol.Soc.,1928,24:480~500
[12]Knopoff L.Energy release in earthquakes.Geophys.J.Roy.Astro.Soc.,1958,1:44~51
[13]Keilis_Borok V I.On estimation of the displacement in an earthquakesource and of source dimensions.Ann.Geofits.,1959,12:205~214
[14]Choy G L,Boatwright J L.Global patterns of radiated seismic energyand apparent stress.J.Geophys.Res.,1995,100:18205~18228
[15]吴忠良,黄静,林碧苍.中国西部地震视应力的空间分布.地震学报,2002,24(3):293~301Wu Z L,Huang J,Lin B C.Distribution of apparent stress inwestern China.Acta Seismologica Sinica(in Chinese),2002,15(3):309~317
[16]McGarr A.On relating apparent stress to the stress causingearthquake fault slip.J.Geophys.Res.,1999,104:3003~3011
[17]陈培善,谷继成,李文香.从断裂力学观点研究地震的破裂过程和地震预报.地球物理学报,1977,20(3):185~202Chen P S,Gu J C,Li W X.A study of the earthquake ruptureprocess and earthquake prediction in the light of fracture mechanics.Chinese J.Geophys.(Acta Geophysica Sinica)(in Chinese),1977,20(3):185~202
[18]陈培善.分析地震波估算地壳内的应力值.地震学报,1981,3(3):251~263Chen P S.An estimation of crustal stress value from analysis ofseismic waves.Acta Seismologica Sinica(in Chinese),1981,3(3):251~263
[19]陈培善,白彤霞,肖磊.根据环境应力场寻找中国大陆地区的潜在地震危险性.地震学报,1995,17(3):294~304Chen P S,Bai T X,Xiao L.In search of potential earthquake sourceregions in the Chinese mainland in the light of ambient shear stressfield.Acta Seismologica Sinica(in Chinese),1995,8(3):365~377
[20]Wyss M,Gillard D,Liang B.An estimate of the absolute stresstensor in Kaoiki,Hawaii.J.Geophys.Res.,1992,97:4763~4768
[21]Aki K,Richards P G.Quantitative seismology:Theory and methods.Vol 1&2,W H Freeman,San Francisco,1980,932
[22]Hauksson E.Crustal structure and seismicity distribution adjacent tothe Pacific and North America plate boundary in Southern California.J.Geophys.Res.,2000,105:13875~13903
[23]Wald D J,Heaton T H.Spatial and temporal distribution of slip forthe 1992 Landers,California earthquake.Bull.Seism.Soc.Amer.,1994,84:668~691
[24]Gephart J W,Forsyth D W.An improved method for determining theregional stress tensor using earthquake focal mechanism data:Application to the San Fernando earthquake sequence.J.Geophys.Res.,1984,89:9305~9320
[25]Gephart J W.FMSI:A FORTRAN program for inverting fault/slickenside and earthquake focal mechanism data to obtain theregional stress tensor.Computer&Geosciences,1990,16:953~989
[26]Hardebeck J L,Hauksson E.Crustal stress field in southernCalifornia and its implications for fault mechanics.J.Geophys.Res.,2001,106:21859~21882
[27]King G C P,Stein R S,Lin J.Static stress changes and thetriggering of earthquakes.Bull.Seism.Soc.Amer.,1994,84:935~953
[28]Troise C,De Natale G,Pingue F,et al.Evidence for static stressinteraction among earthquakes in south_central Apennines(Italy).Geophys.J.Int.,1998,134:809~817
[29]王凯英,马瑾,顾国华等.1996年川滇地区发生的一次应力转向事件.地学前缘,2003,10(S1):233~239Wang K Y,Ma J,Gu G H,et al.Rotation of stress axis in Sichuan_Yunnan region in 1996.Earth Science Frontiers(in Chinese),2003,10(S1):233~239
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