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Bayesian Multi-Model Estimation of Fault Slip Distribution for Slow Slip Events in Southwest Japan: Effects of Prior Constraints and Uncertain Underground Structure
Journal of Geophysical Research: Solid Earth ( IF 3.9 ) Pub Date : 2022-08-08 , DOI: 10.1029/2021jb023712
R. Agata 1 , R. Nakata 2 , A. Kasahara 3 , Y. Yagi 4 , Y. Seshimo 5 , S. Yoshioka 5, 6 , T. Iinuma 1
Affiliation  

We consider a Bayesian multi-model fault slip estimation (BMMFSE), which incorporates many candidates of the underground structure (Earth structure and plate boundary geometry) model characterized by a prior probability density function (PDF). The technique is used to study long-term slow slip events (L-SSEs) that occurred beneath the Bungo Channel, southwest Japan, in around 2010 and 2018. We here focus on the two advantages of BMMFSE: First, it allows for estimating slip distribution without introducing relatively strong prior information such as smoothing constraints, by combining a fully Bayesian inference and better consideration of model uncertainty to avoid overfitting. Second, the posterior PDF for the underground structure is also obtained during the fault slip estimation, which can be used as priors for the estimation of slip distribution for recurring events. The estimated slip distribution obtained using BMMFSE agreed better with the distribution of deep tectonic tremors at the down-dip side of the main rupture area than those based on stronger prior constraints when the corresponding Coulomb failure stress changes are compared. This finding suggests a mechanical relationship between the L-SSE and the synchronized tremors. The use of the posterior PDF of the underground structure estimated for the 2010 L-SSE as prior PDF for the 2018 event resulted in more consistent estimation with the data, indicated by a smaller value of an information criterion.

中文翻译:

日本西南部慢滑动事件断层滑动分布的贝叶斯多模型估计:先验约束和不确定地下结构的影响

我们考虑贝叶斯多模型断层滑动估计(BMMFSE),它结合了许多以先验概率密度函数(PDF)为特征的地下结构(地球结构和板块边界几何)模型的候选者。该技术用于研究 2010 年和 2018 年左右在日本西南部丰后海峡下方发生的长期慢滑动事件 (L-SSE)。我们在这里关注 BMMFSE 的两个优点:首先,它可以估计滑动在不引入相对强的先验信息(例如平滑约束)的情况下,通过结合完全贝叶斯推理和更好地考虑模型不确定性来避免过度拟合。其次,在断层滑动估计过程中还获得了地下结构的后验概率分布函数,它可以用作估计重复事件的滑动分布的先验。当比较相应的库仑破坏应力变化时,使用 BMMFSE 获得的估计滑移分布与主破裂区下倾侧的深部构造震颤分布比基于更强的先验约束的分布更符合。这一发现表明 L-SSE 和同步震颤之间存在机械关系。使用为 2010 年 L-SSE 估计的地下结构的后验概率密度函数作为 2018 年事件的先验概率概率函数导致与数据的估计更一致,由信息标准的较小值表明。当比较相应的库仑破坏应力变化时,使用 BMMFSE 获得的估计滑移分布与主破裂区下倾侧的深部构造震颤分布比基于更强的先验约束的分布更符合。这一发现表明 L-SSE 和同步震颤之间存在机械关系。使用为 2010 年 L-SSE 估计的地下结构的后验概率密度函数作为 2018 年事件的先验概率概率函数导致与数据的估计更一致,由信息标准的较小值表明。当比较相应的库仑破坏应力变化时,使用 BMMFSE 获得的估计滑移分布与主破裂区下倾侧的深部构造震颤分布比基于更强的先验约束的分布更符合。这一发现表明 L-SSE 和同步震颤之间存在机械关系。使用为 2010 年 L-SSE 估计的地下结构的后验概率密度函数作为 2018 年事件的先验概率概率函数导致与数据的估计更一致,由信息标准的较小值表明。
更新日期:2022-08-08
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