A two-dimensional spectral-element method for computing spherical-earth seismograms - I. Moment-tensor source
A two-dimensional spectral-element method for computing spherical-earth seismograms - I. Moment-tensor source
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DOI：
10.1111/j.1365-246x.2006.03121.x
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发表时间：
2007-03-01
影响因子：
2.8
通讯作者：
Dahlen, F. A.
中科院分区：
文献类型：
--
作者：
Nissen-Meyer, Tarje;Fournier, Alexandre;Dahlen, F. A.
我们发展了一种谱单元方法来计算球对称地球模型在二维半圆计算区域中的全三维力矩张量和点力响应。通过求解六个独立的二维问题，即单极震源问题三个，偶极震源问题两个，四极震源问题一个，即可确定震中六分量力矩张量和地震台三分量点力的全部弹性动力响应。这种分而治之的三维到二维的归约策略为球对称地球中精确的Frechet灵敏度核的有效计算提供了基础，其中考虑了所有的波场特征。为了将全源包含在柱坐标系中，我们描述了弹性动力学方程组的二维弱形式，它使用谱单元进行离散，以及在均匀的固体弹性球体的情况下每种激励类型的轴向边界条件和源表示。用解析解和简正波求和方法对该方法进行了数值验证。
We develop a spectral-element method for computing the full 3-D moment-tensor and point-force response of a spherically symmetric earth model in a 2-D semi-circular computational domain. The full elastodynamic response to a six-component moment tensor at an earthquake hypocentre and a three-component point force at a seismic station can be determined by solving six independent 2-D problems, three for a monopole source, two for a dipole source, and one for a quadrupole source. This divide-and-conquer 3-D to 2-D reduction strategy provides a basis for the efficient computation of exact Frechet sensitivity kernels in a spherically symmetric earth, with all wavefield features accounted for. To focus on the novel inclusion of the full source in a cylindrical coordinate system, we describe the 2-D weak formulation of the set of elastodynamic equations, its discretization using spectral elements, and the associated axial boundary conditions and source representations for each of the excitation types in the case of a homogeneous, solid elastic sphere. The method is numerically validated against both analytical solutions and normal-mode summation.