GPS资料揭示的汶川8.0级地震前地壳动态演化特征
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摘要
利用中国大陆1999年以来3个时段的GPS速度场,研究了汶川8.0地震前的地壳动态演化特征。研究结果显示:1)汶川地震发生在区域地壳挤压运动明显受阻的区域,孕震区附近存在一较大的障碍体,震中附近断层多年来处于强闭锁状态;2)随着地震发生日期的临近,震中西侧压性区表现出明显的向东逐步扩张态势,局部地区主压应变方向出现向北偏转,右旋剪切作用明显增强;3)汶川地震同震变形及6级以上余震分布表现出的区段性与断裂带及附近分段性运动变形特征密切相关。
By using the GPS velocity fields of China mainland in three time periods since 1999,the characteristics of crustal dynamic evolution before Wenchuan Ms8.0 earthquake was studied.From the results following knowledges can be drawn.1)The Wenchuan earthquake had taken place in the zone where crustal squeezed movements were blocked obviously.There was a large obstacle existed in the seismogenic zone,and the fault nearby the epicenter was in strong blocking state for many years.2)With the Wenchuan earthquake approaching,the compressive zone in the west to epicenter gradually expanded to east obviously.In some local areas,the direction of principal compressive strain deflected northward,and right lateral shear slip enhanced obviously.3)The sectional features of coseismic deformation in Whenchuan earthquake and 6.0 or more aftershock distribution were closely related to the sectional movement deformation of the fault and its vicinal zone.
By using the GPS velocity fields of China mainland in three time periods since 1999,the characteristics of crustal dynamic evolution before Wenchuan Ms8.0 earthquake was studied.From the results following knowledges can be drawn.1)The Wenchuan earthquake had taken place in the zone where crustal squeezed movements were blocked obviously.There was a large obstacle existed in the seismogenic zone,and the fault nearby the epicenter was in strong blocking state for many years.2)With the Wenchuan earthquake approaching,the compressive zone in the west to epicenter gradually expanded to east obviously.In some local areas,the direction of principal compressive strain deflected northward,and right lateral shear slip enhanced obviously.3)The sectional features of coseismic deformation in Whenchuan earthquake and 6.0 or more aftershock distribution were closely related to the sectional movement deformation of the fault and its vicinal zone.
引文
1江在森,等.汶川8.0级地震前区域地壳运动与变形动态过程[J].地球物理学报,2009,52(2):505-518.(JiangZaisen,et al.The dynamic process of regional crustal move-ment and deformation before WenchuanMs8.0 earthquake[J].Chinese Journal of Geophysics,2009,52(2):505-518)
2张培震,等.2008年汶川8.0级地震发震断裂的滑动速率、复发周期和构造成因[J].地球物理学报,2008,51(4):1 066-1 073.(Zhang Peizhen,et al.Slip rates andrecurrence intervals of the Longmenshan active fault zone andtectonic implications for the mechanism of the May 12 Wen-chuan earthquake,2008,Sichuan,China[J].Chinese Jour-nal of Geophysics,2008,51(4):1 066-1 073)
3黄媛,等.汶川8.0级大地震及其余震序列重定位研究[J].中国科学(D辑),2008,38(10):1 242-1 249.(Huang Yuan,et al.The repositioning research of Wen-chuan 8.0 earthquake and after shock sequence[J].Sciencein China(Series D),2008,38(10):1 242-1 249)
4单新建,等.汶川8.0级地震InSAR同震形变场[J].地球物理学报,2009,52(2):496-504.(Shan Xijian,et al.Co-seismic surface deformation caused by the WenchuanMs8.0earthquake from InSAR data analysis[J].Chinese Journal ofGeophysics,2009,52(2):496-504)
5张希,江在森.对华北地区GPS监测区近期地壳应变连续分布的估计[J].地震学刊,1999,75(2):57-62.(Zhang Xi and Jiang Zaisen.Estimation of resent crustalstrain continuous distribution in GPS monitoring area of theNorth China area[J].Journal of Seismology,1999,75(2):57-62)
6王敏.基于GPS同震位移场约束反演2008年5.12汶川大地震破裂空间分布[J].地球物理学报,2009,52(10):2 519-2 526.(Wang Min.Coseismic displacementdistribution of the 2008 Wenchuan great earthquake con-strained by using GPS coseismic displacement field[J].Chi-nese Journal Geophysics,2009,52(10):2 519-2 526)
7杜方,等.2008年汶川8.0级地震前横跨龙门山断裂带的震间形变[J].地球物理学报,2009,52(11):2 729-2 738.(Du Fang,et al.Interseismic deformation across theLongmenshan fault zone before the 2008M8.0 Wenchuanearthquake[J].Chinese Journal of Geophysics,2009,52(11):2 729-2 738)
2张培震,等.2008年汶川8.0级地震发震断裂的滑动速率、复发周期和构造成因[J].地球物理学报,2008,51(4):1 066-1 073.(Zhang Peizhen,et al.Slip rates andrecurrence intervals of the Longmenshan active fault zone andtectonic implications for the mechanism of the May 12 Wen-chuan earthquake,2008,Sichuan,China[J].Chinese Jour-nal of Geophysics,2008,51(4):1 066-1 073)
3黄媛,等.汶川8.0级大地震及其余震序列重定位研究[J].中国科学(D辑),2008,38(10):1 242-1 249.(Huang Yuan,et al.The repositioning research of Wen-chuan 8.0 earthquake and after shock sequence[J].Sciencein China(Series D),2008,38(10):1 242-1 249)
4单新建,等.汶川8.0级地震InSAR同震形变场[J].地球物理学报,2009,52(2):496-504.(Shan Xijian,et al.Co-seismic surface deformation caused by the WenchuanMs8.0earthquake from InSAR data analysis[J].Chinese Journal ofGeophysics,2009,52(2):496-504)
5张希,江在森.对华北地区GPS监测区近期地壳应变连续分布的估计[J].地震学刊,1999,75(2):57-62.(Zhang Xi and Jiang Zaisen.Estimation of resent crustalstrain continuous distribution in GPS monitoring area of theNorth China area[J].Journal of Seismology,1999,75(2):57-62)
6王敏.基于GPS同震位移场约束反演2008年5.12汶川大地震破裂空间分布[J].地球物理学报,2009,52(10):2 519-2 526.(Wang Min.Coseismic displacementdistribution of the 2008 Wenchuan great earthquake con-strained by using GPS coseismic displacement field[J].Chi-nese Journal Geophysics,2009,52(10):2 519-2 526)
7杜方,等.2008年汶川8.0级地震前横跨龙门山断裂带的震间形变[J].地球物理学报,2009,52(11):2 729-2 738.(Du Fang,et al.Interseismic deformation across theLongmenshan fault zone before the 2008M8.0 Wenchuanearthquake[J].Chinese Journal of Geophysics,2009,52(11):2 729-2 738)
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