九江—瑞昌序列震源位置及震源区速度结构的联合反演
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摘要
采用震源位置和速度结构的联合反演方法确定2005年九江—瑞昌5.7级地震序列的分布和震源区的速度结构。结果显示九江—瑞昌地震序列存在NW330°方向和NE55°方向的两组共轭分布,其中NW330°方向的优势分布更为明显;震源深度分布在3～18km的范围,地震主体破裂发生在上地壳—中地壳过渡层的P波速度低速区内,主震发生后余震向东南与西北方向两头扩展,其中往西北方向破裂时可能遇到了障碍体,积累的能量转向西南—北东方向继续破裂,引发了4.8级强余震。
The hypocentral locations and velocity structure of the 2005 Jiujiang -Ruichang Ms5.7 earthquake sequence have been identified using the simultaneous inversion method. The results show that this sequence displays two conjugated distributions at the directions of NW330° and NE55° respectively,but the former is more obvious. The focal depths vary from 3km to 18km and the main rupture occurred in the low P wave velocity zone of the upper -middle crust transition layer. Aftershocks developed along the southeast and northwest directions,but the latter probably encountered an asperity,and continued to rupture along the southeast -northeast direction and triggered the MS4.8 strong aftershock.
The hypocentral locations and velocity structure of the 2005 Jiujiang -Ruichang Ms5.7 earthquake sequence have been identified using the simultaneous inversion method. The results show that this sequence displays two conjugated distributions at the directions of NW330° and NE55° respectively,but the former is more obvious. The focal depths vary from 3km to 18km and the main rupture occurred in the low P wave velocity zone of the upper -middle crust transition layer. Aftershocks developed along the southeast and northwest directions,but the latter probably encountered an asperity,and continued to rupture along the southeast -northeast direction and triggered the MS4.8 strong aftershock.
引文
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[14]吕坚,倪四道,沈小七,等.九江一瑞昌地震的精确定位及其发震构造初探[J].中国地震,2007,23(2):166-174.
[15]吕坚,郑勇,倪四道,等.2005年11月26日九江-瑞昌MS5.7、MS4.8地震的震源机制解与发震构造研究[J].地球物理学报,2008,51(1):158-164.
[2]Thurber,C.H.Earthquake locations and three-dimensional crustal structure in the Coyote late area,Central California[J].J.Geophys.Res.,1983,88:8226-8236.
[3]刘福田.震源位置和速度结构的联合反演(I)——理论和方法[J].地球物理学报,1984,27(2):167-175.
[4]Pavlis,L.G.and Booker,J.R.The mixed discrete-continuous inverse problem:application to the simultaneous determination of earthquake hypocenters and velocity structure[J].J.Geophys.Res.,1980,85:4801-4810.
[5]Spencer,C.and Gubbins,D.Travel time inversion for simultaneous earthquake location and velocity structure determination in laterally varying media[J].Geophys.J.R.Astron.Soc.,1980,63(1):95-116.
[6]Geiger,L.Probability method for the determination of earthquake epicenters from arrival time only[J].Bull.St.Louis.Univ.,1912,8:60-71.
[7]Zhao,D.,Hasegawa,A.and Horiuchi,S.Tomographic imaging of P and S wave velocity structure beneath northeastern Japan[J].J.Geophys.Res,1992,97:19909-19928.
[8]周龙泉,刘杰,陈晓非,等.2003年大姚6.2、6.1级地震前三维波速结构的演化[J].地震学报,2007,29(1):20-30.
[9]王椿镛,张先康,丁志峰,等.大别造山带上部地壳结构的有限差分层析成像[J].地球物理学报,1997,40(4):495-502.
[10]王椿镛,张先康,陈步云,等.大别造山带地壳结构研究[J].中国科学(D辑),1997,27(3):221-226.
[11]Paige,C.C.and Saunders,M.A.LSQR:Sparse linear equations and least squares problems[J].ACM Transactions on Mathematical Software,1982,8(2):195-209.
[12]Zhou,H.Direct inversion of velocity interfaces[J].Geophys Res Lett,2004,7:doi:10.1029/2003GL019318.
[13]杨明桂,王昆.江西省地质构造格架及地壳演化[J].江西地质,1994,8(4):239-251.
[14]吕坚,倪四道,沈小七,等.九江一瑞昌地震的精确定位及其发震构造初探[J].中国地震,2007,23(2):166-174.
[15]吕坚,郑勇,倪四道,等.2005年11月26日九江-瑞昌MS5.7、MS4.8地震的震源机制解与发震构造研究[J].地球物理学报,2008,51(1):158-164.
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