Modelling two-dimensional global seismic wave propagation in a laterally heterogeneous whole-Moon model
Modelling two-dimensional global seismic wave propagation in a laterally heterogeneous whole-Moon model
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在横向异质全月模型中模拟二维全球地震波传播
DOI：
10.1093/gji/ggs094
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发表时间：
2013-01
影响因子：
2.8
通讯作者：
Jianshe Lei
中科院分区：
文献类型：
--
作者：
Yanbin Wang;Hiroshi Takenaka;Xianghua Jiang;Jianshe Lei
最近通过重新分析月球地震数据提出了全月模型，该模型假定地震波在月球内有效传播。然而，在以强混响和尾波为特征的月震信号中，常见的地震体波或地震表面波相不存在或非常弱。因此，地震波在月球内部的传播过程并不能从有限的月球地震数据中得到很好的理解。基于最近发表的全月模型，对地震体波在全月的传播进行了数值模拟。本文采用交错网格拟谱和有限差分混合法求解球面月球二维剖面中的地震波方程。我们的模拟结果提供了地震体波在整个月球的传播过程，无论是深，浅月震与连续波场快照和合成波形。通过模拟月球层析成像模型，研究了横向非均匀性对地震波传播的影响。与观测到的阿波罗地震图的比较表明，模拟预测了directPandS波的到来，并再现了直接波和二次波的混响性质。然而，如果模型中没有考虑其他可能的因素，如散射，仅用1-D或层析模型建模似乎不足以产生观测中的能量缓慢衰减。不同震源机制的对比表明，直达波有很大的差异，但结构模型对合成地震记录的整体特征有很大的贡献。数值模拟表明，有效的传播和相互作用的地震体波在整个月球的各种接口。地震能量在近地表低速层中传播形成的陷波沿地表沿着传播，在波形中表现为混响。混响的强度随着主频率和焦深的减小而增加。在未来的月球地震实验中，应通过部署甚宽频带地震计网络来提高月球地震体波相位的可探测性，这将进一步提高我们对月球内部的认识。
The whole-Moon model was recently proposed by re-analyzing of lunar seismic data, which presumes efficient propagation of seismic waves within the Moon. However, common seismic body-wave or surface-wave phases observed for earthquake are absent or very weak in lunar seismic signals characterized by strong reverberations and coda. Hence, the process of seismic wave propagation in the Moon's interior is not well understood from limited lunar seismic data. We present numerical simulations of seismic body wave propagation in the whole Moon based on recently published whole-Moon model. Seismic wave equations are solved in a 2-D cross-section of spherical Moon with a staggered grid pseudospectral and finite difference hybrid method. Our simulation results provide the processes of seismic body wave propagation in the whole Moon for both deep and shallow moonquakes with sequential wavefield snapshots and synthetic waveforms. Effects of lateral heterogeneity on seismic wave propagation were investigated by simulations for a Moon tomographic model. Comparisons with the observed Apollo seismograms show that simulations predicted the arrivals of directPandSwaves and reproduced the reverberating nature of both direct and secondary waves. However, modelling with only the 1-D or tomographic model does not seem to be enough to produce the slow decay of energy in observations if other possible factors, such as scattering, are not considered in the model. Comparisons between different focal mechanisms suggest that great differences can be seen for the direct waves, but the structure model contributes significantly to the overall characteristics of synthetic seismograms. Numerical simulations demonstrated efficient propagation and interactions with various interfaces of seismic body waves within the whole Moon. Seismic energy propagating in the near surface low-velocity layer formed trapped waves, which propagate along the surface and appear as reverberations in the waveforms. Strength of the reverberations increases with dominant frequency and decreasing focal depth. Detectability of lunar seismic body-wave phases should be enhanced with deployment of very broad band seismometer network in the future lunar seismic experiment, which will further improve our knowledge of the Moon's interior.
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影响因子：
--
作者：
J. Edgell
通讯作者：
J. Edgell
影响因子：
25.2
作者：
M. Toksöz;A. Dainty;Sean C. Solomon;Kenneth R. Anderson
通讯作者：
M. Toksöz;A. Dainty;Sean C. Solomon;Kenneth R. Anderson
影响因子：
2.3
作者：
Yosio Nakamura
通讯作者：
Yosio Nakamura
DOI：
10.1016/c2009-1-28330-4
发表时间：
2007
期刊：
--
影响因子：
--
作者：
G. Schubert
通讯作者：
G. Schubert
影响因子：
--
作者：
Amir Khan;K. Mosegaard
通讯作者：
Amir Khan;K. Mosegaard