Development of monitoring and forecasting methods for crustal activity utilizing large-scale high-fidelity finite element simulations with 3D heterogeneous medium

Takane Hori, Tsuyoshi Ichimura, Kohei Fujita, Takuma Yamaguchi, Takeshi Iinuma, & Ryoichiro Agata

Published August 14, 2018, SCEC Contribution #8476, 2018 SCEC Annual Meeting Poster #030 (PDF)

To analyse crustal activity in the Earth's interior, such as spatio-temporal variation in slip velocity on the plate/fault interfaces including ordinary and slow earthquakes, we need to use the data observed mostly on the Earth's surface. If the data are limited far from the deformation sources, it would be enough to use simple model as elastic half space. However, it is becoming intrinsic to consider 3D heterogeneous structure of the interior, especially in subduction zone, since we can obtain dense surface deformation data on land and partly on the sea floor, just above the sources. Thus, to fully utilize such fruitful data, it is necessary to develop physics-based data analysis methods including (1) a structural model with the 3D geometry of the plate/fault interfaces and the material property such as elasticity and viscosity, (2) calculation codes for crustal deformation and seismic wave propagation using (1), (3) inverse analysis codes both for structure and fault slip using (1) and (2). To accomplish these, it is at least necessary to develop highly reliable large-scale simulation codes to calculate crustal deformation and seismic wave propagation for 3D heterogeneous structure. Unstructured finite element (FE) non-linear seismic wave simulation code has been developed (Ichimura et al. [2015]). A high-fidelity FE simulation code with mesh generator has also been developed to calculate crustal deformation in and around Japan with complicated surface topography and subducting plate geometry for 1km mesh (Ichimura et al. [2016]). This code has been improved for higher resolution in calculation of crustal deformation and achieved 2.05 T-DOF with 45m resolution on the plate interface (Fujita et al. [2016]). This high-resolution analysis enables evaluation of stress change acting on the plate interface. For inverse analyses, waveform inversion code for modeling 3D crustal structure has been developed (Ichimura et al. [2017]). Furthermore, such large-scale simulation codes have been implemented on the GPU clusters and analysis tools have been developed to estimate fault slip distribution with considering uncertainty in structural models (Yamaguchi et al. [2017a,b]). Utilizing them, we are developing the data assimilation method for monitoring and forecasting the slip velocity variation on the plate/fault interfaces with 3D heterogeneous structure. We have been modeled subduction zones in Japan and are planning to model southern California fault systems.

Citation
Hori, T., Ichimura, T., Fujita, K., Yamaguchi, T., Iinuma, T., & Agata, R. (2018, 08). Development of monitoring and forecasting methods for crustal activity utilizing large-scale high-fidelity finite element simulations with 3D heterogeneous medium. Poster Presentation at 2018 SCEC Annual Meeting.

Related Projects & Working Groups
Collaboratory for Interseismic Simulation and Modeling (CISM)