Bayesian Inversion for a Stress‐Driven Model of Afterslip and Viscoelastic Relaxation: Method and Application to Postseismic Deformation Following the 2011 Mw 9.0 Tohoku‐Oki Earthquake
Bayesian Inversion for a Stress‐Driven Model of Afterslip and Viscoelastic Relaxation: Method and Application to Postseismic Deformation Following the 2011 Mw 9.0 Tohoku‐Oki Earthquake
复制标题
应力驱动后滑和粘弹性松弛模型的贝叶斯反演：2011 年 Mw 9.0 东北冲地震震后变形的方法和应用
DOI：
10.1029/2020jb021620
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Johnson Kaj M.
中科院分区：
文献类型：
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作者：
Fukuda Junichi;Johnson Kaj M.
大俯冲地震后的震后变形通常被建模为大逆冲断层上的后掠角和地幔中同震应力变化的粘弹性松弛的贡献之和。然而，它通常是很难分开的贡献，这些机制的大地测量观测震后变形。在这里，我们开发了一种反演方法，用于估计应力驱动的震后变形模型的参数，该模型采用同震和震后大地测量数据，将速度加强后滑和粘弹性地幔松弛由双粘性Burgers流变学控制。我们假设后滑和粘弹性松弛是由同震应力变化驱动的，并相互作用。待估计的未知参数包括驱动震后过程的同震滑动分布，以及断层摩擦和地幔粘度参数。我们提出了一个贝叶斯制定的反问题和算法估计后验概率密度函数。这种方法使我们能够量化模型参数的不确定性。我们将该方法应用于2011年东北冲地震的同震位移和震后位移时间序列。我们的研究结果表明，观测对模型参数有严格的约束，估计的模型有效地再现了震后水平和垂直变形的一阶空间和时间模式。我们发现，余震滑动和粘弹性松弛的水平和垂直震后变形的相对贡献在空间上不同。我们认为，我们的方法可能提供一种客观地分离这两种机制对震后变形的贡献的方法。
Postseismic deformation following great subduction earthquakes is commonly modeled as the sum of the contributions from afterslip on the megathrust and viscoelastic relaxation of the coseismic stress changes in the mantle. However, it is generally difficult to separate the contributions of these mechanisms to geodetically observed postseismic deformation. Here we develop an inversion method for estimating the parameters of a stress‐driven postseismic deformation model that incorporates velocity‐strengthening afterslip and viscoelastic mantle relaxation governed by a biviscous Burgers rheology using coseismic and postseismic geodetic data. We assume that afterslip and viscoelastic relaxation are driven by coseismic stress changes and interact mechanically with each other. The unknown parameters to be estimated include the coseismic slip distribution that drives the postseismic processes, and the fault frictional and mantle viscosity parameters. We present a Bayesian formulation of the inverse problem and an algorithm for estimating the posterior probability density function. This approach allows us to quantify the uncertainties of the model parameters. We apply the method to the coseismic displacements and postseismic displacement time series of the 2011 Tohoku‐Oki earthquake. Our results show that the observations place tight constraints on the model parameters, with the estimated model effectively reproducing the first‐order spatial and temporal patterns of horizontal and vertical postseismic deformation. We find that the relative contributions of afterslip and viscoelastic relaxation to horizontal and vertical postseismic deformation vary in space. We suggest that our method may potentially provide a way to objectively separate the contributions of these two mechanisms to postseismic deformation.