根据地震定标律研究汶川8.0级地震的破裂特征
|
摘要
根据二维地震位错模式导出的地震定标律关系,估算了汶川8.0级地震的断层破裂参数和震源应力参数,结果给出:主破裂断层长度L=218km,破裂宽度W=29km,断层破裂面积S=6310km2,最大位错D=5.01m,断层破裂速度vr=2.8km/s,主破裂过程持续时间为78s,地震矩M0=7.94×1020N.m,矩震级MW=7.9,这些断层破裂参数与有关的研究结果基本一致。对主震和3次6级强余震的震源应力参数进行了估算,结果给出:主震应力降Δσ=6.34MPa,视应力σa=0.60MPa,剪应力τ0=22.13MPa,表明主震的发震应力场处于构造环境剪应力为22.13MPa的高值背景,主震发生后,6级强余震剪应力τ0下降了约一半,平均约为10MPa;应力降Δσ则没有明显变化,平均为7.0MPa左右。结合余震序列空间分布情况,分析认为主震破裂为单侧破裂,走向为NE方向,断层从初始破裂点开始主破裂长度约200km范围内是地震能量主要的释放区,由于主震为浅源大震,震源离地表较近,因而在破裂过程中释放的巨大地震波能量对震区造成了烈度高达Ⅺ度的破坏。
Based on seismic scaling law from two-dimensional faulting model,we estimate the fault rupture parameters of the MS8.0 Wenchuan earthquake.The length of fault is 18 km,the width 29 km,the area 6 310 km2,the maximum offset 5.01 m,the rupturing velocity 2.8 km/s,the duration of rupture process 78 s,the seismic moment 7.94×1020 N·m,the moment magnitude 7.9,which are basically consistent with the results of related studies.We also calculate the focal stress parameters of the mainshock and three strong aftershocks with M≥6.The stress drop of main shock is 6.34 MPa,the apparent stress 0.60 MPa,the shear stress 22.13 MPa,which shows the high tectonic ambient shear stress for the main shock.The average shear stress of the M≥6 aftershocks is about 10 MPa,about one half of the mainshock;the stress drops have no apparent changes,and the average is about 7.0 MPa.Combined with the distribution of aftershocks,the fault plane of the main shock is unilateral rupture and rupture trend is in NE.The main release region of seismic energy is about 200 km from the initial fault rupture.Because the mainshock is shallow and large and the seismic source near the surface,the enormous seismic energy released by the mainshock during the rupture process cause the destruction with Ⅺ degree intensity in the seismic area.
Based on seismic scaling law from two-dimensional faulting model,we estimate the fault rupture parameters of the MS8.0 Wenchuan earthquake.The length of fault is 18 km,the width 29 km,the area 6 310 km2,the maximum offset 5.01 m,the rupturing velocity 2.8 km/s,the duration of rupture process 78 s,the seismic moment 7.94×1020 N·m,the moment magnitude 7.9,which are basically consistent with the results of related studies.We also calculate the focal stress parameters of the mainshock and three strong aftershocks with M≥6.The stress drop of main shock is 6.34 MPa,the apparent stress 0.60 MPa,the shear stress 22.13 MPa,which shows the high tectonic ambient shear stress for the main shock.The average shear stress of the M≥6 aftershocks is about 10 MPa,about one half of the mainshock;the stress drops have no apparent changes,and the average is about 7.0 MPa.Combined with the distribution of aftershocks,the fault plane of the main shock is unilateral rupture and rupture trend is in NE.The main release region of seismic energy is about 200 km from the initial fault rupture.Because the mainshock is shallow and large and the seismic source near the surface,the enormous seismic energy released by the mainshock during the rupture process cause the destruction with Ⅺ degree intensity in the seismic area.
引文
陈培善,白彤霞.1991.震源参数之间的定量关系[J].地震学报,13(4):401-411.
陈培善,肖磊,白彤霞,等.1994.唐山地震序列的环境应力场[J].地震学报,16(4):441-447.
陈学忠,李艳娥,郭祥云.2008.2008年5月12日四川汶川8.0级地震前后震源区应力水平估计[J].国际地震动态,(6):1-3.
成尔林.1981.四川及其邻区现代构造应力场和现代构造运动特征[J].地震学报,3(3):231-241.
钱晓东,秦嘉政,叶建庆.2006.云南地区的环境应力参数及其在地震短临预报中的应用[J].地震研究,29(1):7-12.
秦嘉政,刘祖荫.1997.用地震标定律研究丽江7.0级地震的破裂过程[J].地震研究,20(1):47-57.
秦嘉政,钱晓东,张俊伟.2000.武定地震序列剪应力场的时空分布特征[J].地震研究,22(1):8-16.
秦嘉政,钱晓东.2006.云南地区地震视应力的时间和空间分布研究[J].地震学报,28(3):221-229.
肖亮,韩鹏,靳超宇,等译.2008.USGS中汶川地震情况[J].国际地震动态,(6):16-26.
许忠淮.2001.东亚地区现今构造应力图的编制[J].地震学报,23(5):492-501.
Bir d P and Li Y.1996.Interpolation of principal stress direction by non-parametric statistics:Global maps with confidence limits[J].JGR,101:5435-5443.
L it hgow-Bertelloni C and Guynn J H.2004.Origin of the lithosphericstress field[J].JGR,109(B0148):1-32.
L ag Tand Kanamori H.2005.The great Sumatra-Andaman earthquake of26December2004[J].Science,308:1127-1133.
Z o back ML.1992.First-and secord-order pattern of stress in the lithes-phere:the world stress project[J].JGR,97(B8):117030-11728.
陈培善,肖磊,白彤霞,等.1994.唐山地震序列的环境应力场[J].地震学报,16(4):441-447.
陈学忠,李艳娥,郭祥云.2008.2008年5月12日四川汶川8.0级地震前后震源区应力水平估计[J].国际地震动态,(6):1-3.
成尔林.1981.四川及其邻区现代构造应力场和现代构造运动特征[J].地震学报,3(3):231-241.
钱晓东,秦嘉政,叶建庆.2006.云南地区的环境应力参数及其在地震短临预报中的应用[J].地震研究,29(1):7-12.
秦嘉政,刘祖荫.1997.用地震标定律研究丽江7.0级地震的破裂过程[J].地震研究,20(1):47-57.
秦嘉政,钱晓东,张俊伟.2000.武定地震序列剪应力场的时空分布特征[J].地震研究,22(1):8-16.
秦嘉政,钱晓东.2006.云南地区地震视应力的时间和空间分布研究[J].地震学报,28(3):221-229.
肖亮,韩鹏,靳超宇,等译.2008.USGS中汶川地震情况[J].国际地震动态,(6):16-26.
许忠淮.2001.东亚地区现今构造应力图的编制[J].地震学报,23(5):492-501.
Bir d P and Li Y.1996.Interpolation of principal stress direction by non-parametric statistics:Global maps with confidence limits[J].JGR,101:5435-5443.
L it hgow-Bertelloni C and Guynn J H.2004.Origin of the lithosphericstress field[J].JGR,109(B0148):1-32.
L ag Tand Kanamori H.2005.The great Sumatra-Andaman earthquake of26December2004[J].Science,308:1127-1133.
Z o back ML.1992.First-and secord-order pattern of stress in the lithes-phere:the world stress project[J].JGR,97(B8):117030-11728.
版权所有：© 2023 中国地质图书馆 中国地质调查局地学文献中心