震源对地震动空间相关性影响的定量研究
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摘要
在震源为线性破裂断层模型的假定下，本文根据震源理论和波谱随空间坐标的展开式，定量分析了震源对地震动空间相关性的影响，得到了场地上相距为d的αb两点地震动的Fourier谱的关系式为Ab（f）＝Aα（f）exp（α1δr0＋α2δθ）。其中，α1，α2为与震源参数、介质特性和场地位置相关并随频率变化的两个复数．δr0与δθ为与台站相对位置有关的参数．本文绘出了计算α1和α2的理论公式，并对α1和α2的物理意义进行了讨论．在此基础上，本文也得到了根据α1和α2估计地震动场孔径的理论公式，最后，以一次M＝6单侧破裂地震为例．通过数值积分，计算α1～α2和孔径防震中矩、方位角和频率变化的三维图像．
Assuming that the seismic source is a linear fault along one-directional rupture,the authors quantitatively analyze the effect of seisdric souree on the space correlation of strong ground motion based on the seismic source theory and expansion of Fourier spectrum of seismic motion with space coordinate variables, and obtain a relation of Fourier spectra at two points a and b of a site with a distance d, that is Ab(f) =Aα (f) exp (α1δr0 + α2δθ),α1 and α2 are two complex numbers which are related to seismin source parameters, media properties, space coordinates of the site as well as frequency. δr0 and δθ are two parameters which are mainly related to relative local space coordinates of sites. This paper presents the theoretical formula calculating α1 and α2, discusses the physical significance of α1 and α2, and obtains a formula for estimating the radius of strong ground motion field based on α1 and α2Finally, taking an earthquake with magnitude 6.0 as an example, the authors calculate threedimensional patterns of α1 and α2 with epicenter distance, direction angle and frequency based on numerical integration, and give the radius variation of the field with frequency.
Assuming that the seismic source is a linear fault along one-directional rupture,the authors quantitatively analyze the effect of seisdric souree on the space correlation of strong ground motion based on the seismic source theory and expansion of Fourier spectrum of seismic motion with space coordinate variables, and obtain a relation of Fourier spectra at two points a and b of a site with a distance d, that is Ab(f) =Aα (f) exp (α1δr0 + α2δθ),α1 and α2 are two complex numbers which are related to seismin source parameters, media properties, space coordinates of the site as well as frequency. δr0 and δθ are two parameters which are mainly related to relative local space coordinates of sites. This paper presents the theoretical formula calculating α1 and α2, discusses the physical significance of α1 and α2, and obtains a formula for estimating the radius of strong ground motion field based on α1 and α2Finally, taking an earthquake with magnitude 6.0 as an example, the authors calculate threedimensional patterns of α1 and α2 with epicenter distance, direction angle and frequency based on numerical integration, and give the radius variation of the field with frequency.
引文
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[2] Abrahamson N A.,Bolt B A,Darragh R B,Penzien J,and Tsai Y B.The SMART-1 Accelerograph Arrary(1980-1987) A Review[J], Earthquake Spectra, Vol.3, No.2. 1987.
[3]Abrahamson N A. Schneider J E. and Stepp J C. Empirical spatial coherency functions for application tosoil-structure interaction analysis[J], Earthquake Spectra, Vol.7, No.1, 1991.
[4]Abrahamson N A. Generation of spatially incoherent strong motion time history[C].Tenth world conlerence onearthquake engineering Madrid, Spain 845～ 850, 1992.
[5]Yamazaki Y, Turke T. Spatial variation study on earthquake ground motion observed by the Chiba array[C].Tenthworld conference on Earthquake Engineering, Madrid, Spain, 651～ 656, 1992.
[6]Katayama T, Yamazaki F. Nagata S, Lu L, and Turker T, A strong Motion database for the Chiba seismometerArrary and its Engineering analysis[J].E.E.S.D,Vol.19,1089-1106,1990.
[7]金星.重大工程场地设计地震动与地震动场的研究[D].博士学位论文,国家地震局工程力学研究所,1992
[8]金星.廖振鹏. 地震动随机场的物理模拟[J].地震工程工程振动, VOl.14, No.3, 1994
[9]李小军,赵凤新,胡聿贤. 空间相关地震动标模型的研究[J].地震学报,Vol. 19,No.2,212-215, 1997.
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