Two-dimensional coda Q structure beneath Tohoku, NE Japan
Two-dimensional coda Q structure beneath Tohoku, NE Japan
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日本东北部地下的二维尾波 Q 结构
DOI：
10.1111/j.1365-246x.1989.tb02018.x
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发表时间：
1989
影响因子：
2.8
通讯作者：
A. Hasegawa
中科院分区：
文献类型：
--
作者：
S. Matsumoto;A. Hasegawa
在单次散射模型上，从尾波振幅的时间衰减估计几个频带的尾波Q值（Q1）。Q，值显示了Q，mf”形式的区域变化和频率依赖性，其中n为0.6-1.2。本文提出了一种估算二维Q_1结构的方法，以研究日本本州岛东北部东北地区Q_1值的区域变化。在空间上分布的每个网格点处的Q值通过对具有适当加权因子的许多事件-站对的观测Q值求平均来估计。通过考虑该网格点对尾波的能量贡献量来计算事件-站对的每个网格点的加权因子。所得到的二维Q_i结构与S波速度结构、Q_i结构以及该区地震活动有一定的关系。低Q_3区一般倾向于对应于低S波速度、低Q_3值和高地震活动区，而高Q_3区则倾向于对应于高S波速度、高Q_3值和低地震活动区。在活火山周围和日本海沿岸附近，Q值相对较低，而在太平洋沿岸附近，Q值相对较高。在短周期地震图上，我们可以看到P波和S波直接到达之后的相当大的地震能量。这部分能量称为地震尾波，可以解释为弹性介质中随机分布的散射体的散射能量。有人提出了一个单散射模型来解释尾波的起源（阿基1969;阿基& Chouet 1975）。根据该模型，尾波是由于介质中的横向不均匀性而向后向散射一次的波的叠加，并且Q值可以根据尾波能量的时间衰减来估计为频率的函数。Sat 0（1977）导出了尾波能量密度时空分布的理论公式，指出尾波能量的时间衰减与震源距离和直达波的射线路径无关。由尾波振幅的时间衰减估计的Q值表示由于散射和本征吸收的组合能量损失。我们可以用散射Q值（Qi）和内禀Q值（Qi）来表示尾波Q值（Qi），其形式为（Dainty 1981）：Qi '= Qi'+ Qi-'。
SUMMARY on the single scattering model, coda-Q values (Q,) are estimated for several frequency bands from the time decay of coda wave amplitude. The Q, value shows a regional variation and frequency dependency of the form Q, mf”, where n is found to be 0.6-1.2. A method for estimating the 2-D Q, structure has been developed to investigate the regional variation of the Q, value beneath Tohoku, the NE part of Honshu, Japan. The Q, value at each grid point spatially distributed is estimated by averaging the observed Q, values for many event-station pairs with adequate weighting factors. The weighting factor at each grid point for an event-station pair is calculated by taking into account the amount of energy contribution to the coda wave from that grid point. The obtained 2-D Q, structure shows some relation to the S-wave velocity structure, the Q, structure and the seismic activity in this area. In general, low Q, regions have a tendency to correspond to the regions with low S-wave velocity, low Q, value and high seismic activity, while high Q, regions correspond to those with high S-wave velocity, high Qs value and low seismic activity. In the regions around active volcanoes and near the coast of the Japan Sea the Q, value is relatively low, whereas it is relatively high near the coast of the Pacific Ocean. On short-period seismograms we can see considerable seismic energy after the direct P- and S-wave arrivals. The energy in this part, which is called seismic coda, can be interpreted as scattered energy from randomly distributed scatterers in an elastic medium. A single scattering model has been proposed to interpret the origin of the coda wave (Aki 1969; Aki & Chouet 1975). According to this model, the coda wave is a superposition of the waves scattered once to the backward direction due to lateral heterogeneity in the medium, and Q values can be estimated as a function of frequency from the time decay of coda wave energy. Sat0 (1977) derived a theoretical formula for the space-time distribution of the energy density of the coda wave, and showed that the time decay of coda wave energy is independent of hypocentral distance and of the ray-path of direct wave through the medium. The Q value estimated from the time decay of coda wave amplitude represents the combined energy loss due to scattering and intrinsic absorption. We can express the coda Q value (Q,) in terms of scattering Q value (Q,) and intrinsic Q value (Qi) in the form (Dainty 1981): Q,’= Q;’ + Q,-’.
日本地下三维纵波和横波速度结构
DOI：
--
发表时间：
2008
期刊：
Phys. Earth Planet. Inter. 168
影响因子：
--
作者：
Chow;et al.;Nakamura M.
通讯作者：
Nakamura M.