No abstract

No abstract

Integrated earthquake simulation (IES) is a seamless simulation of analyzing all processes of earthquake hazard and disaster. There are two difficulties in carrying out IES, namely, the requirement of large-scale computation and the requirement of numerous analysis models for structures in an urban area, and they are solved by taking advantage of high performance computing (HPC) and by developing a system of automated model construction. HPC is a key element in developing IES, as it needs to analyze wave propagation and amplification processes in an underground structure; a model of high fidelity for the underground structure exceeds a degree-of-freedom larger than 100 billion. Examples of IES for Tokyo Metropolis are presented; the numerical computation is made by using K computer, the supercomputer of Japan. The estimation of earthquake hazard and disaster for a given earthquake scenario is made by the ground motion simulation and the urban area seismic response simulation, respectively, for the target area of 10,000 m × 10,000 m.

No abstract

We study the stability of the solutions of the governing equations for soil liquefaction, assuming perturbations in the form of plane wave and of spherical wave. We model the dilatancy effect of soil for stability analysis by setting relevant components of constitutive tensors. Theoretical analysis shows that perturbations in the form of plane wave are always stable without dilatancy and can be unstable when dilatancy ratios exceed a certain critical value. We derive the critical dilatancy ratio explicitly for the plane wave case. For perturbations in the form of spherical wave, numerical simulations reveal similar dependency of stability on dilatancy ratios. As the existence of unstable solution is confirmed, our analysis provides a new perspective on possible initiation of liquefaction: a transition from stable to unstable solutions of the governing equations.