利用多个震源机制解求祁连山西段平均应力场方向
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摘要
祁连山西段由于受到多个构造块体的共同约束,表现出复杂的地球物理特性和地质特性。本文利用14个中强地震震源机制解和2001-2012年66个中小地震震源机制解分析了区域应力场特征。结果显示,地震的震源性质以走滑和逆冲为主,印证了祁连山西段基本构造变形特征;三个区域应力张量的定量结果显示,最大主压应力σ1方向在NE向,水平挤压作用明显,且具有一定的分区特征,表明局部应力场受到局部构造的影响。
The western segment of the Qilian Mountains,which is controlled by some tectonic blocks,has complicated geography and geology.This study looked at 14 strong-moderate earthquakes and 66 small-moderate earthquakes from 2001 to 2012,used the stress tensor averaging method to calculate the direction of the mean stress axis in the area,and then analyzed the characteristics of the stress field.Moreover,we compared the results with another inversion result by using the FMSI inversion process.Finally,we conducted a detailed study of the tectonic stress field characteristics of the western segment of the Qilian Mountains. With the stress tensor calculation method,we obtained the average direction of T,B,and P axes by calculating the average stress tensor of focal mechanism solutions from multiple earthquakes.If the earthquake has a relatively independent discrete distribution in the block,we can deduce the direction of the principal stress axes in the regional tectonic stress field on the basis of the average direction of T,B,and P axes. In our research,we selected two groups of data,strong-moderate earthquakes and small-moderate earthquakes from 2001 to 2012.We obtained 14 focal mechanism solutions for strong-moderate earthquakes occurring since 1900,with 4 above MS6.0 and 10 between MS5.0 and MS5.9.Furthermore,another was the earthquake that occurred on December 25,1932,the large Changma MS7.6 in the western Changma fault.In addition,we used the CAP method and the vertical P-wave and S-wave amplitude ratio method to calculate the focal mechanisms of small-moderate earthquakes. The focal mechanisms show that the characteristics of focus are mainly strike-slip and thrust earthquakes.The quantification results for stress tensor in three regions show that the azimuth of maximum principal compressive stress,σ1,is NE,and the horizontally compressed acts show evidence of definite subarea characteristics.
The western segment of the Qilian Mountains,which is controlled by some tectonic blocks,has complicated geography and geology.This study looked at 14 strong-moderate earthquakes and 66 small-moderate earthquakes from 2001 to 2012,used the stress tensor averaging method to calculate the direction of the mean stress axis in the area,and then analyzed the characteristics of the stress field.Moreover,we compared the results with another inversion result by using the FMSI inversion process.Finally,we conducted a detailed study of the tectonic stress field characteristics of the western segment of the Qilian Mountains. With the stress tensor calculation method,we obtained the average direction of T,B,and P axes by calculating the average stress tensor of focal mechanism solutions from multiple earthquakes.If the earthquake has a relatively independent discrete distribution in the block,we can deduce the direction of the principal stress axes in the regional tectonic stress field on the basis of the average direction of T,B,and P axes. In our research,we selected two groups of data,strong-moderate earthquakes and small-moderate earthquakes from 2001 to 2012.We obtained 14 focal mechanism solutions for strong-moderate earthquakes occurring since 1900,with 4 above MS6.0 and 10 between MS5.0 and MS5.9.Furthermore,another was the earthquake that occurred on December 25,1932,the large Changma MS7.6 in the western Changma fault.In addition,we used the CAP method and the vertical P-wave and S-wave amplitude ratio method to calculate the focal mechanisms of small-moderate earthquakes. The focal mechanisms show that the characteristics of focus are mainly strike-slip and thrust earthquakes.The quantification results for stress tensor in three regions show that the azimuth of maximum principal compressive stress,σ1,is NE,and the horizontally compressed acts show evidence of definite subarea characteristics.
引文
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[8]钟继茂,程万正.由多个地震震源机制解求川滇地区平均应力场方向[J].地震学报,2006,28(4):337-346.ZHONG Ji-mao,CHENG Wan-zheng.Determination of Direc-tions of the Mean Stress Field in Sichuan-Yunnan Regionfrom A Number of Focal Mechanism Solutions[J].Acta Seis-mologica Sinica,2006,28(4):337-346.
[9]刘泽民,刘东旺,李玲利,等.利用多个震源机制解求东大别地区平均应力场[J].地震学报,2011,33(5):605-613.LIU Ze-ming,LIU Dong-wang,LI Ling-li,et al.Determinationof Mean Stress Field in Eastern Dabie Region from FocalMechanism Solution Analysis[J].Acta Seismologica Sinica,2001,33(5):605-613.
[10]唐兰兰,赵翠萍,王海涛.2008年新疆乌恰6.8级地震序列震源特征及帕米尔东北缘应力场研究[J].地球物理学报,2012,55(4):1228-1239.TANT Lan-lan,ZHAO Cui-ping,WANG Hai-tao.Study onthe Source Characteristics of the 2008 MS6.8 Wuqia,Xin-jiang Earthquake Sequence and the Stress Field on the North-eastern Boundary of Pamir[J].Chinese J.Geophys.,2012,55(4):1228-1239.
[11]朱弟成,潘桂棠,莫宣学,等.印度大陆和欧亚大陆的碰撞时代[J].地球科学进展,2004,19(4):564-571.ZHU Di-cheng,PAN Gui-tang,MO Xuan-xue,et al.The Ageof Collision between India and Eurasia[J].Advances in EarthScience,2004,19(4):564-571.
[12]莫宣学,赵志丹,周肃,等.印度-亚洲大陆的碰撞时限[J].地质通报,2007,26(10):1240-1244.MO Xuan-xue,ZHao Zhi-dan,ZHOU Su,et al.On the Tim-ing of India-Asia Continental Collision[J].Geological Bulle-tin of Chia,2007,26(10):1240-1244.
[13]葛肖红,刘俊来.北祁连造山带的形成与背景[J].地学前缘,I999,6(4):223-230.GE Xiao-hong,LIU Jun-lai.Formation and Tectonic Back-ground of the Northern Qilian Orogentic Belt[J].Earth Sci-ence Frontiers,1999,6(4):223-230.
[14]陈柏林,刘建生.祁连山北缘-河西走廊地区大地形变与地震的关系[J].地质通报,2009,28(10):1439-1447.CHEN Be-lin,LIU Jian-sheng.Geodetic Deformation inNorthern Qilianshan Margin and Hexi Corridor Area,North-west China and Its Relation to the Earthquake[J].GeologicalBulletin of China,2009,28(10):l439-1447.
[15]王萍,卢演俦,陈杰.阿尔金断裂东端的旋转构造及其动力学意义[J].中国地震,2004,20(2):134-142.WANG Ping,LU Yin-chou,CHEN Jie.Tectonic Transfor-mation in the Eastern Part of the Altun Fault[J].EarthquakeResearch in China,2004,20(2):134-142.
[16]徐纪人,赵志新,石川有三.中国大陆地壳应力场与构造运动区域特征研究[J].地球物理学报,2008,51(3):770-781.XU Ji-ren,ZHAO Zhi-xin,Ishikawa Yuzo.Regional Charac-teristics of Crustal Stress Field and Tectonic Motions in andaround Chinese Mainland[J].Chinese J.Geophys.,2008,51(3):770-781.
[17]许忠淮.东亚地区现今构造应力图的编制[J].地震学报,2001,23(5):492-501.XU Zhong-huai.A present-day Tectonic Stress Map forEastern Asia Region[J].Acta Seismologica Sinica,2001,23(5):492-501.
[18]Zhu L,Helmberger D V.Advancement in Source EstimationTechniques Using Broadband Regional Seismograms[J].Bull.Seism.Soc.Am.,1996,86:1634-1641.
[19]Zhu L,Tan Y,Helmberger D V,et al.Calibration of the Ti-betan Plateau Using Regional Seismic Waveforms[J].Pa-geoph,2006,163:1193-1213.
[20]张辉,徐辉,姚军,等.祁连山中东段基于CAP方法的中小地震震源机制研究[J].山西地震,2010,(1):25-29.ZHANG Hui,XU Hui,YAO Jun,et al.Study on SourceMechanism of Small-to-moderate Earthquakes Based on CAPMethod in Middle-eastern Segment of Qilian Mountain[J].Shanxi Earthquake,2010,(1):25-29.
[21]梁尚鸿,李幼铭,束沛镒,等.利用区域地震台网P、S振幅比资料测定小震震源参数[J].地球物理学报,1984,27(3):249-256.LIANG Shang-hong,LI You-ming,SHU Pei-yi,et al.On theDetermining of Source parameters of Small Earthquakes byUsing Amplitude Ratios of P and S from Regional NetworkObservations[J].Chinese J.Geophys.,1984,27(3):249-256.
[22]马宗晋,张家声,汪一鹏.青藏高原三维变形运动学的时段划分和新构造分区[J].地质学报,1998,72(3):211-227.MA Zong-jin,ZHANG Jia-sheng,WANG Yi-peng.The 3-DDeformational Movement Episodes and Neotectonic Domainsin the Qinghai-Tibet Plateau[J].Acta Geologica Sinica,1998,72(3):211-327.
[23]Gan W,Zhang P,Shen Z K,et al.Present-day Crustal Motionwithin the Tibetan Plateau Inferred from GPS Measurements[J].J.geophys.Res.,2007,112:B8416.
[24]Zhao L S,Helmberger D V.Source Estimation from Broad-band Regional Seismograms[J].Bull.Seis.Soc.Amer.,1994,84(1):91-104.
[2]Yamakawa N,山川宜男.Stress Field in Focal Regions[J].J.Phys.Earth,1971,19:347-353.
[3]许忠淮.用滑动方向拟合法反演唐山余震区的平均应力场[J].地震学报,1985,7(4):349-361.XU Zhong-huai.Mean Stress Field in Tangshan AftershockArea Obtained from Focal Mechanism Data by Fitting Slip Di-rections[J].Acta Seismologica Sinica,1985,7(4):349-361.
[4]Boot M H P.The Mechanics of Oblique Slip Faulting[J].Geo-logical Magazine,1959,96(2):109-117.
[5]Gephart J W,Forsyth D W.An Improved Method for Deter-mining the Regional Stress Tensor Using Earthquake FocalMechanism Data:Application to the San Fernand EarthquakeSequence[J].J.Geop.hys.Res.,1984,89:9305-9320.
[6]许忠淮,戈澍谟.用滑动方向拟合法反演富蕴地震断裂带应力场[J].地震学报,1984,6(4):395-404.XU Zhong-huai,GE Shu-mo.Stress Field in the Fuyun,Xin-jiang Earthquake Fracture Zone Determined by Fitting FaultSlip Vector Data[J].Acta Seismologica Sinica,1984,6(4):395-404.
[7]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[J].地震学报,1999,21(5):513-522.CUI Xiao-feng,XIE Fu-ren.Preliminary Research to Deter-mine Stress Districts from Focal Mechanism in Southwest Chi-na and Its Adjacent Area[J].Acta Seismologica Sinica,1999,21(5):513-522.
[8]钟继茂,程万正.由多个地震震源机制解求川滇地区平均应力场方向[J].地震学报,2006,28(4):337-346.ZHONG Ji-mao,CHENG Wan-zheng.Determination of Direc-tions of the Mean Stress Field in Sichuan-Yunnan Regionfrom A Number of Focal Mechanism Solutions[J].Acta Seis-mologica Sinica,2006,28(4):337-346.
[9]刘泽民,刘东旺,李玲利,等.利用多个震源机制解求东大别地区平均应力场[J].地震学报,2011,33(5):605-613.LIU Ze-ming,LIU Dong-wang,LI Ling-li,et al.Determinationof Mean Stress Field in Eastern Dabie Region from FocalMechanism Solution Analysis[J].Acta Seismologica Sinica,2001,33(5):605-613.
[10]唐兰兰,赵翠萍,王海涛.2008年新疆乌恰6.8级地震序列震源特征及帕米尔东北缘应力场研究[J].地球物理学报,2012,55(4):1228-1239.TANT Lan-lan,ZHAO Cui-ping,WANG Hai-tao.Study onthe Source Characteristics of the 2008 MS6.8 Wuqia,Xin-jiang Earthquake Sequence and the Stress Field on the North-eastern Boundary of Pamir[J].Chinese J.Geophys.,2012,55(4):1228-1239.
[11]朱弟成,潘桂棠,莫宣学,等.印度大陆和欧亚大陆的碰撞时代[J].地球科学进展,2004,19(4):564-571.ZHU Di-cheng,PAN Gui-tang,MO Xuan-xue,et al.The Ageof Collision between India and Eurasia[J].Advances in EarthScience,2004,19(4):564-571.
[12]莫宣学,赵志丹,周肃,等.印度-亚洲大陆的碰撞时限[J].地质通报,2007,26(10):1240-1244.MO Xuan-xue,ZHao Zhi-dan,ZHOU Su,et al.On the Tim-ing of India-Asia Continental Collision[J].Geological Bulle-tin of Chia,2007,26(10):1240-1244.
[13]葛肖红,刘俊来.北祁连造山带的形成与背景[J].地学前缘,I999,6(4):223-230.GE Xiao-hong,LIU Jun-lai.Formation and Tectonic Back-ground of the Northern Qilian Orogentic Belt[J].Earth Sci-ence Frontiers,1999,6(4):223-230.
[14]陈柏林,刘建生.祁连山北缘-河西走廊地区大地形变与地震的关系[J].地质通报,2009,28(10):1439-1447.CHEN Be-lin,LIU Jian-sheng.Geodetic Deformation inNorthern Qilianshan Margin and Hexi Corridor Area,North-west China and Its Relation to the Earthquake[J].GeologicalBulletin of China,2009,28(10):l439-1447.
[15]王萍,卢演俦,陈杰.阿尔金断裂东端的旋转构造及其动力学意义[J].中国地震,2004,20(2):134-142.WANG Ping,LU Yin-chou,CHEN Jie.Tectonic Transfor-mation in the Eastern Part of the Altun Fault[J].EarthquakeResearch in China,2004,20(2):134-142.
[16]徐纪人,赵志新,石川有三.中国大陆地壳应力场与构造运动区域特征研究[J].地球物理学报,2008,51(3):770-781.XU Ji-ren,ZHAO Zhi-xin,Ishikawa Yuzo.Regional Charac-teristics of Crustal Stress Field and Tectonic Motions in andaround Chinese Mainland[J].Chinese J.Geophys.,2008,51(3):770-781.
[17]许忠淮.东亚地区现今构造应力图的编制[J].地震学报,2001,23(5):492-501.XU Zhong-huai.A present-day Tectonic Stress Map forEastern Asia Region[J].Acta Seismologica Sinica,2001,23(5):492-501.
[18]Zhu L,Helmberger D V.Advancement in Source EstimationTechniques Using Broadband Regional Seismograms[J].Bull.Seism.Soc.Am.,1996,86:1634-1641.
[19]Zhu L,Tan Y,Helmberger D V,et al.Calibration of the Ti-betan Plateau Using Regional Seismic Waveforms[J].Pa-geoph,2006,163:1193-1213.
[20]张辉,徐辉,姚军,等.祁连山中东段基于CAP方法的中小地震震源机制研究[J].山西地震,2010,(1):25-29.ZHANG Hui,XU Hui,YAO Jun,et al.Study on SourceMechanism of Small-to-moderate Earthquakes Based on CAPMethod in Middle-eastern Segment of Qilian Mountain[J].Shanxi Earthquake,2010,(1):25-29.
[21]梁尚鸿,李幼铭,束沛镒,等.利用区域地震台网P、S振幅比资料测定小震震源参数[J].地球物理学报,1984,27(3):249-256.LIANG Shang-hong,LI You-ming,SHU Pei-yi,et al.On theDetermining of Source parameters of Small Earthquakes byUsing Amplitude Ratios of P and S from Regional NetworkObservations[J].Chinese J.Geophys.,1984,27(3):249-256.
[22]马宗晋,张家声,汪一鹏.青藏高原三维变形运动学的时段划分和新构造分区[J].地质学报,1998,72(3):211-227.MA Zong-jin,ZHANG Jia-sheng,WANG Yi-peng.The 3-DDeformational Movement Episodes and Neotectonic Domainsin the Qinghai-Tibet Plateau[J].Acta Geologica Sinica,1998,72(3):211-327.
[23]Gan W,Zhang P,Shen Z K,et al.Present-day Crustal Motionwithin the Tibetan Plateau Inferred from GPS Measurements[J].J.geophys.Res.,2007,112:B8416.
[24]Zhao L S,Helmberger D V.Source Estimation from Broad-band Regional Seismograms[J].Bull.Seis.Soc.Amer.,1994,84(1):91-104.
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