Ryoichiro Agata

Robust and portable capacity computing method for many finite element analyses of a high-fidelity crustal structure model aimed for coseismic slip estimation

Computation of many Greens functions (GFs) in finite element (FE) analyses of crustal deformation is an essential technique in inverse analyses of coseismic slip estimations. In particular, analysis based on a high-resolution FE model (high-fidelity model) is expected to contribute to the construction of a community standard FE model and benchmark solution. Here, we propose a naive but robust and portable capacity computing method to compute many GFs using a high-fidelity model, assuming that various types of PC clusters are used. The method is based on the master-worker model, implemented using the Message Passing Interface (MPI), to perform robust and efficient input/output operations. The method was applied to numerical experiments of coseismic slip estimation in the Tohoku region of Japan; comparison of the estimated results with those generated using lower-fidelity models revealed the benefits of using a high-fidelity FE model in coseismic slip distribution estimation. Additionally, the proposed method computes several hundred GFs more robustly and efficiently than methods without the master-worker model and MPI. HighlightsA coseismic slip estimation method using a high-fidelity crust model was proposed.Computation of many Greens functions (GFs) is essential for the inverse analyses.A robust and portable capacity computing method for many GFs was developed.The application example demonstrated the benefit of use of a high-fidelity model.The proposed method computed many GFs robustly and efficiently.

Numerical Verification Criteria for Coseismic and Postseismic Crustal Deformation Analysis with Large-scale High-fidelity Model

Abstract Numerical verification of postseismic crustal deformation analysis, computed using a large-scale finite element simulation, was carried out, by proposing new criteria that consider the characteristics of the target phenomenon. Specifically, pointwise displacement was used in the verification. In addition, the accuracy of the numerical solution was explicitly shown by considering the observation error of the data used for validation. The computational resource required for each analysis implies that high- performance computing techniques are necessary to obtain a verified numerical solution of crustal de- formation analysis for the Japanese Islands. Such verification in crustal deformation simulations should take on greater importance in the future, since continuous improvement in the quality and quantity of crustal deformation data is expected.

Several Hundred Finite Element Analyses of an Inversion of Earthquake Fault Slip Distribution using a High-fidelity Model of the Crustal Structure☆

To improve the accuracy of inverse analysis of earthquake fault slip distribution, we performed several hundred analyses using a 108-degree-of-freedom finite element (FE) model of the crustal structure in an efficient way based on capacity computing. we developed a meshing method and an efficient computational method for these large FE models, which methods are specialized for the problem setting. We applied the model to the inverse analysis of coseismic fault slip distribution for the 2011 Tohoku-oki Earthquake. The high resolution of our model provided a significant improvement of the fidelity of the simulation results compared to existing computational approaches.

Tsunami Analysis Method with High-Fidelity Crustal Structure and Geometry Model

Higher fidelity seafloor topography and crustal structure models have become available with accumulation of observation data. Previous studies have shown that the consideration of such high-fidelity models produces significant effects, in some cases, on crustal deformation results that are used as inputs for tsunami analysis. However, it is difficult to apply high-fidelity model of crustal deformation computations to tsunami computations because of large computational costs. In this paper, we propose a new crustal deformation computation method for estimating inputs for tsunami computations, which is based on a finite element analysis method with remarkable reduction of computation costs by efficient use of the arithmetic space and the solution space. This finite element analysis method enables us to conduct 102−3-times crustal deformation computations using high-fidelity models with a degree of freedom on the order of 108 for the 2011 Tohoku earthquake example. Tsunami computations with typical settings are conducted as an application example to present the advantages and characteristics of the proposed method. Comparisons between results of the proposed and the conventional method reveal that large shallow fault slip around the trench axis may lead to significant differences in tsunami waveforms and inundation height distributions in some cases.