长周期地脉动观测在深部地层调查中的应用
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摘要
对上海软土地区的长周期地脉动信号进行观测,采用傅里叶频谱分析及微动水平与垂直速度分量(H/V)频谱分析相关理论,分析地脉动信号的频谱稳定性及卓越频率的空间变化规律,通过反演分析得到沉积土层厚度及其横向变化规律,并与已知钻孔资料加以对比.结果表明:适宜在上海地区深入展开长周期地脉动测试,其长周期地脉动信号稳定;H/V频谱曲线峰值显著,并且在长周期范围内呈现出规律性的变化特征;上海地区软土层厚度为200~300 m.
The long period microtremor observation was performed on soft soil area in Shanghai city.The FFT spectrum analysis and H/V method were used to evaluate the spatial variations of long period microtremor and its spectrum stability and clarify the depth of deposits and its horizontal distributions.Comparing the inversion results with the known borehole data,the signal of long period microtremor is good and it is very appropriate to deeply expand the investigations in Shanghai city,the signal of microtrmor in the long period area is steady;the peak of H/V spectrum is obvious and shows regular variation characteristic which reveals the depth of soil in Shanghai city is between 200 m and 300 m.
The long period microtremor observation was performed on soft soil area in Shanghai city.The FFT spectrum analysis and H/V method were used to evaluate the spatial variations of long period microtremor and its spectrum stability and clarify the depth of deposits and its horizontal distributions.Comparing the inversion results with the known borehole data,the signal of long period microtremor is good and it is very appropriate to deeply expand the investigations in Shanghai city,the signal of microtrmor in the long period area is steady;the peak of H/V spectrum is obvious and shows regular variation characteristic which reveals the depth of soil in Shanghai city is between 200 m and 300 m.
引文
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[2]师黎静,陶夏新,赵纪生.地脉动台阵方法的有效性分析[J].岩石力学与工程学报,2006,25(8):1683-1690.SHI Li-jing,TAO Xia-xin,ZHAO Ji-sheng.Validationof microtremors array method[J].Chinese Journal ofGeotechnical Engineering,2006,25(8):1683-1690.
[3]李智玲.表层微动的基本原理及在抗震工作中的作用[M].北京:地震出版社,1991:198-202.
[4]Castro R R.S-waves site-response estimates usinghorizontal-to-vertical spectral ratios[J].Bull Seism SocAm,1997,87:256-260.
[5]杨学林,陈云敏,蔡袁强.利用地脉动确定地基自振频率[J].岩土工程学报,1995,17(4):51-55.YANG Xue-lin,CHEN Yun-min,CAI Yuan-qiang.Determining the natural frequency by microtremors[J].Chinese Journal of Geotechnical Engineering,1995,17(4):51-55.
[6]Nakamura Y.A method for dynamic characters esti-mation of subsurface using microtremors on the groundsurface[R].R of RTRI 30,1989:25-33.
[7]Seekins L,Wennerberg L,Mwrgheriti,et al.Siteamplification at five locations in San Francisco,Cali-fornia,a comparison of S-waves,codas and micro-tremors[J].BullSeism Soc Am,1996,86:627-635.
[8]Sophia Hassiotis,Jeong Garrett D.Identification ofstiffness reductions using natural frequencies[J].Journal of Engineering Mechanics,1995,10:1106-1113.
[9]上海市地质调查研究院.上海地球物理勘探技术应用与发展[M].上海:上海科技出版社,2010:165-167.
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