Study on scattering and seismic-wave envelopes in short-periods in the heterogeneous medium

阐明固体地球介质的非均匀性对研究地球演化过程具有重要意义。速度不均匀性的频谱可以被认为是很宽的，因此，散射过程的测量是必要的研究具有相同的地震波的波长尺度的不均匀性。重点讨论了随机介质中波传播的数学基础，以及从短周期地震波的观测特征来度量地球介质非均匀性。本文的主要成果如下：（1）根据马尔可夫近似，成功地建立了层状随机介质表面短周期矢量波包络的合成公式。(2)We根据小地震S波包络分析估算日本本州东北地区地下的随机速度不均匀性，其中速度不均匀性很强，特别是在第四纪火山下面。（3）从 ...更多信息 根据多次各向同性散射模型，对Hi-net记录的近震S波波形包络进行了分析，阐明了日本S波散射损失和本征吸收的区域性变化。（4）根据辐射传输理论对火山爆发地震图的分析，估算出浅磨火山在10 Hz时的平均自由程约为1 km，比岩石圈中的平均自由程强两个数量级。(5)By利用玻恩近似，证明了散射介质中由噪声互相关函数反演绿色函数的方法。然后证明了当噪声源在空间随机均匀分布时，散射介质的绿色函数反演与广义光学定理的等价性。(6)We出版了一本教科书，汇编了短周期地震波的观测特征和随机非均匀地球介质中波散射的数学理论。少

It is important to clarify the medium heterogeneity of the solid earth for the study of the evolution process of the earth. The spectra of the velocity inhomogeneity can be considered to be very broad ; therefore, measurements of scattering process is necessary for the study of inhomogeneity having the same scale of the wavelength of seismic waves. We put a focus on the mathematical bases of the wave propagation through random media and the measurement of the earth medium heterogeneity from the characteristics of observed seismic waves in short periods. We enumerate the obtained results as follows :(1)We successfully formulated the synthesis of vector-wave envelopes in short periods on the surface of layered random media according to the Markov approximation.(2)We estimated random velocity inhomogeneities beneath Tohoku, Honshu, Japan from the envelope analysis of S-waves of small earthquakes, where the velocity inhomogeneity is strong especially beneath Quaternary volcanoes.(3)From th … More e analysis of S-seismogram envelopes of local earthquakes registered by Hi-net on the basis of the multiple isotropic scattering model, we clarified the regional variation of scattering loss and intrinsic absorption of S-waves in Japan.(4)From the analysis of explosion seismograms according to the radiative transfer theory, we estimated the mean free path beneath Asamo volcano to be as small as 1 km at 10 Hz, which is two order stronger than that in the lithosphere.(5)By using the Born approximation, we proved the Green function retrieval from the noise cross correlation function for a scattering medium. Then we proved the equivalence of the Green function retrieval and the generalized optical theorem for a scattering medium when the distribution of noise sources is random and uniform in space.(6)We published a textbook which compiles the characteristics of observed seismic waves in short periods and mathematical theories on scattering of waves in the randomly heterogeneous earth medium. Less