Effect of fault discretization on geodetic source inversion and usefulness of the trans-dimensional inversion approach
Effect of fault discretization on geodetic source inversion and usefulness of the trans-dimensional inversion approach
复制标题
断层离散化对大地源反演的影响和跨维反演方法的实用性
DOI：
10.1093/gji/ggab515
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发表时间：
2022
影响因子：
2.8
通讯作者：
Noda Akemi
中科院分区：
文献类型：
--
作者：
Kubo Hisahiko;Suzuki Wataru;Noda Akemi
震源反演是根据地球物理资料估计断层上的非均匀滑动分布，是估计地震破裂过程和获取断层破裂物理信息的基础技术。震源反演需要对断层进行空间离散化，离散化可以是均匀的，也可以是非均匀的。均匀断层离散化是一种常规方法，其需要滑动的平滑和/或非负约束作为先验信息以获得稳定且可靠的解;然而，均匀离散化和这些先验约束的组合可能使源反演解失真。作为一种非均匀离散化方法，使用跨维反演方法的震源反演最近引起了人们的关注。为研究断层离散化对大地源反演的影响，通过对2015年尼泊尔廓尔喀地震大地测量数据的分析和综合试验，研究了均匀离散化常规源反演和跨维源反演的解以及解的不确定性。我们发现，均匀离散化和非负约束的组合导致过于光滑的解决方案与不良的数据拟合。即使不使用非负约束，传统的反演与均匀离散提供扭曲的，有时过拟合的解决方案，这不能识别的基础上的不确定性信息。相比之下，跨维源反演提供了合理的解决方案，只包括有意义的滑移，这是解释数据所必需的。我们还发现，不确定性信息取决于源反演方法，因此，方法引起的不确定性的评估是困难的。这表明，我们通过震源反演的透镜来观察地震破裂，这种反演具有固有的方法依赖性偏差。
Earthquake source inversion, which estimates the heterogeneous slip distribution on fault from geophysical data, is a fundamental technique for estimating earthquake rupture process and obtaining information about the physics of fault rupture. Source inversion requires the spatial discretization of fault, which can be performed uniformly and non-uniformly. Uniform fault discretization is a conventional approach that requires smoothing and/or non-negative constraints of slips as prior information to obtain a stable and reliable solution; however, the combination of uniform discretization and these prior constraints may distort a source-inversion solution. As a non-uniform discretization approach, source inversion using a trans-dimensional inversion approach has recently attracted attention. To study the effect of fault discretization on geodetic source inversion, through the analysis of geodetic data on the 2015 Gorkha, Nepal, earthquake and synthetic tests, we investigated what kind of solution the conventional source inversion with uniform discretization and the trans-dimensional source inversion provide and what kind of uncertainty their solutions have. We found that the combination of uniform discretization and non-negative constraint led to excessively smooth solutions with poor data fit. Even without using the non-negative constraint, the conventional inversion with uniform discretization provided distorted and sometimes overfitted solutions, which could not be identified based on uncertainty information. In contrast, the trans-dimensional source inversion provided reasonable solutions composed only of meaningful slips, which were required to explain the data. We also found that uncertainty information depends on the source-inversion method; consequently, the evaluation of method-induced uncertainty is difficult. This suggests that we look at earthquake ruptures through the lens of source inversion with inherent method-dependent bias.