Unified approach to amplitude attenuation and coda excitation in the randomly inhomogeneous lithosphere   总被引：2，自引：0，他引：2  

Haruo Sato 《Pure and Applied Geophysics》1990,132(1-2):93-121

A unified model is proposed for explaining the frequency dependent amplitude attenuation and the coda wave excitation on the basis of the single scattering process in the randomly inhomogeneous lithosphere. Adopting Birch's law and a direct proportion between density and wave velocity, we statistically describe the inhomogeneous medium by one random function characterized by the von Karman autocorrelation function. We calculate the amplitude attenuation from the solid angle integral of scattered wave energy on the basis of the Born approxiimation after subtracting the travel-time fluctuation effect caused by slowly varying velocity inhomogeneities. This subtraction is equivalent to neglect energy loss by scattering within a cone around the forward direction. The random inhomogeneity of the von Karman autocorrelation function of order 0.35 with the mean square fractional fluctuation of 7.2×10^–3 1.3×10^–2 and the correlation distance of 2.15.1 km well explains observed backward scattering coefficientg and the ratioQ _P ^–1 /Q _S ^–1 , and observed and partially conjecturedQ _S ^–1 for frequencies between 0.5 Hz and 30 Hz.  相似文献   

Separation of intrinsic and scattering seismic attenuation in the Southern Apennine zone, Italy   总被引：4，自引：0，他引：4  

F. Bianco  E. Del Pezzo  M. Castellano  J. Ibanez  F. Di Luccio 《Geophysical Journal International》2002,150(1):10-22

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Distribution of L_g coda Q in the Chinese continent and its adjacent regions     

丛连理  胡家富  傅竹武  温一波  康国发  吴小平 《中国科学D辑(英文版)》2003,46(6)

In continent Lg is usually one of the predominant phases recorded by short-period or broad-band seismometers. A ray-theoretical approach shows that Lg wave is the superposition of higher-mode surface waves propagating in the continental crust[1—4]. The g…  相似文献   

Time-domain computation of scattering from a heterogeneous layer     

Xiaofan Li  J. A. Hudson 《Geophysical Journal International》1997,128(1):197-203

Adopting Born and ray approximations, time-domain synthetic seismograms for P-P and P-S scattering from a plane wave incident on a thin, laterally heterogeneous layer are presented in this paper. The time-domain P coda is a convolution between a structure function and the second-order derivative of the time function of the incident P wave. Examples of synthetic seismograms are given using a time function from a computed short-period seismogram for a point explosive source in a half-space. These show that it is impossible, with realistic values of the parameters involved, to generate significant codas when only single scattering is involved.  相似文献   

Deconvolution of teleseismic recordings for mantle structure     

M. G. Bostock  M. D. Sacchi 《Geophysical Journal International》1997,129(1):143-152

Delineation of detailed mantle structure frequently requires the separation of source signature and structural response from seismograms recorded at teleseismic distances. This deconvolution problem can be posed in a log-spectral domain where the operation of time-domain convolution is reduced to an additive form. The introduction of multiple events recorded at many stations leads to a system of consistency equations that must be honoured by both the source time functions and the impulse responses associated with propagation paths between sources and receivers. The system is inherently singular, and stabilization is accomplished through the supply of an initial estimate of the source time function. Although alternative choices exist, an effective estimate is derived from the eigenimage associated with the largest eigenvalue in a singular-value decomposition of the suite of aligned seismograms corresponding to a given event. The relation of the deconvolution scheme to simultaneous least-squares deconvolution is examined. Application of the methodology to broadband teleseismic P waveforms recorded on the Canadian National Seismograph Network demonstrates the retrieval of effective Green's functions including secondary phases associated with upper-mantle structure.  相似文献   

Attenuation of coda waves and Q _c value beneath the Chengdu telemetered seismic network     

Jian Zeng  Tian-Chang Chen  Wei-Bin Han  Jun Fan  Si-Hua Zheng  Akira Hasegawa  Shigeki Horiuchij  Satoshi Matsumoto 《地震学报(英文版)》1997,10(3):313-320

Based on the single scattering model of coda power spectrum analysis, digital waveform data of 50 events recorded by the real-time processing system of the Chengdu telemetry network are analyzed to estimate the Q _c values of earth medium beneath the Chengdu telemetry network for several specified frequencies. It is found that the Q _c shows the frequency dependency in the form of Q _c = Q ₀ f ⁿ in the range of 1.0 to 20.0Hz. Estimated Q ₀ ranges from 60.83 to 178.05, and n is found to be 0.713 to 1.159. The average value of Q ₀ and n are 117 and 0.978 respectively. This result indicates the strong frequency dependency of the attenuation of coda waves beneath the Chengdu telemetry network. Comparing with the results obtained in other regions of the world, it is found that Q ₀ ⁻¹ value and its change with frequency are similar to those in regions with strong tectonic activity. This subject is supported by the Ministry of Personnel, China for partly sponsoring.  相似文献   

The coda attenuation of the Yao''''an area in Yunnan Province   总被引：1，自引：0，他引：1  

李白基  秦嘉政  钱晓东  叶建庆 《地震学报(英文版)》2004,17(1):47-53

IntroductionThetravellingqualityfactorQofseismicwaveisoneofbasicphysicalparametersformeasuringthemediaattenuation(1/Q)intheearthandreflectionofinhomogeneityandinelasticityofthemedia,whichisusedinstudiesoffocalphysicsandengineeringearthquake.Qiscloselyrelatedtotheregionaltectonicactivityandseismicity.Thisfeaturehasbeenstudyingasoneoffactorsofearthquakeprediction(Chouet,1979;JinandAki,1986,1989).InYunnanregion,QIN(1992)andQIN,etal(1995)hadstudiedthefeaturesofregionalvariationofcodaQcandflu…  相似文献   

Simulation of seismic response in a city-like environment   总被引：1，自引：0，他引：1  

Jean-Philippe Groby  Chrysoula Tsogka  Armand Wirgin   《Soil Dynamics and Earthquake Engineering》2005,25(7-10):487-504

We study the seismic response of idealized 2D cities, constituted by non-equally spaced, non-equally sized homogenized blocks anchored in a soft layer overlying a hard half space. The blocks and soft layer are occupied by dissipative media. To simulate such response, we use an approximation of the viscoelastic modulus by a low-order rational function of frequency and incorporate this approximation into a first-order-in-time scheme. Our results display spatially variable, strong, long-duration responses inside the blocks and on the ground, which qualitatively match the responses observed in some earthquake-prone cities of Mexico, France, the USA, etc.  相似文献   

Coda-derived source spectra, moment magnitudes and energy-moment scaling in the western Alps     

P. Morasca  K. Mayeda  L. Malagnini  William R. Walter 《Geophysical Journal International》2005,160(1):263-275

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用叠加谱比法研究新疆地区Lg尾波Q值的区域性变化     

徐彦  毛燕  胡家富  苏有锦  丛连理 《云南地理环境研究》2005,17(2):6-10,27

运用叠加谱比法,对分布于新疆地区的5个台站所记录的51个地震数据进行分析,得出与各射线路径相对应的Lg尾波Q0(Lg尾波在1Hz处的Q)值。结果表明:Q0值呈现出明显的区域性变化特点,与构造活动关系紧密。在较为稳定的塔里木地台,Q0呈现出高值,在350～450之间。在南部构造活动较为激烈的昆仑褶皱系,Q0呈现出较低的值,约为200～250。在构造活动最为激烈的帕米尔地区,Q0值在170～200之间。在北部的天山褶皱系,Q0值约为220～270。准葛尔褶皱系比天山褶皱系的Q0值略高,约为260～290。  相似文献