Spectral-infinite-element simulations of earthquake-induced gravity perturbations
Spectral-infinite-element simulations of earthquake-induced gravity perturbations
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DOI：
10.1093/gji/ggz028
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发表时间：
2019-04
影响因子：
2.8
通讯作者：
H. N. Gharti;L. Langer;J. Tromp
中科院分区：
文献类型：
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作者：
H. N. Gharti;L. Langer;J. Tromp
虽然经常观察到地震引起的重力扰动，但这一现象的数值建模仍然是一个挑战。由于缺乏可靠和通用的数值工具，诱导重力数据尚未被充分利用来约束震源参数。从数值的角度来看，主要的挑战来自于支配重力扰动的无界泊松/拉普拉斯方程。此外，泊松/拉普拉斯方程必须与控制固体中粒子位移的线性动量守恒方程耦合。大多数现有的方法要么在完全球谐表示中求解耦合方程，这要求模型是（近）球对称的，要么在球谐域中求解泊松/拉普拉斯方程，在离散域中求解动量方程，这是一种折衷精度和效率的策略。我们提出了一种谱无限元方法，它结合了高精度和高效率的谱元方法与映射无限元方法，能够模仿一个无限域，而不增加显着的内存或计算成本。我们在完全离散的域中求解完整的耦合动量-引力方程，使我们能够在不影响精度或效率的情况下适应复杂的现实模型。我们提出了几个同震和震后的例子和基准同震的例子对大久保的解析解。最后，我们考虑重力扰动引起的1994年北岭地震南加州的3-D模型。算例表明，我们的方法非常准确、高效，并且对于地震后模拟是稳定的。
Although earthquake-induced gravity perturbations are frequently observed, numerical modelling of this phenomenon has remained a challenge. Due to the lack of reliable and versatile numerical tools, induced-gravity data have not been fully exploited to constrain earthquake source parameters. From a numerical perspective, the main challenge stems from the unbounded Poisson/Laplace equation that governs gravity perturbations. Additionally, the Poisson/Laplace equation must be coupled with the equation of conservation of linear momentum that governs particle displacement in the solid. Most existing methods either solve the coupled equations in a fully spherical harmonic representation, which requires models to be (nearly) spherically symmetric, or they solve the Poisson/Laplace equation in the spherical harmonics domain and the momentum equation in a discretized domain, a strategy that compromises accuracy and efficiency. We present a spectral-infinite-element approach that combines the highly accurate and efficient spectral-element method with a mapped-infinite-element method capable of mimicking an infinite domain without adding significant memory or computational costs. We solve the complete coupled momentum-gravitational equations in a fully discretized domain, enabling us to accommodate complex realistic models without compromising accuracy or efficiency. We present several coseismic and post-earthquake examples and benchmark the coseismic examples against the Okubo analytical solutions. Finally, we consider gravity perturbations induced by the 1994 Northridge earthquake in a 3-D model of Southern California. The examples show that our method is very accurate and efficient, and that it is stable for post-earthquake simulations.