Abstract: Data-intensive science frontiers and challenges are emerging as computer technology has evolved substantially. Large-scale simulations demand significant I/O workload, and as a result the I/O performance often becomes a bottleneck preventing high performance in scientific applications. In this paper we introduce a variety of I/O optimization techniques developed and implemented when scaling a seismic application to petascale. These techniques include file system striping, data aggregation, reader/writer limiting and less interleaving of data, collective MPI-IO, and data staging. The optimizations result in nearly perfect scalability of the target application on some of the most advanced petascale systems. The techniques introduced in this paper are applicable to other scientific applications facing similar petascale I/O challenges.

Abstract: Physics-based earthquake disaster simulations are expected to contribute to high-precision earthquake disaster prediction; however, such models are computationally expensive and the results typically contain significant uncertainties. Here we describe Monte Carlo simulations where 10,000 calculations were carried out with stochastically varied building structure parameters to model 3,038 buildings. We obtain the spatial distribution of the damage caused for each set of parameters, and analyze these data statistically to predict the extent of damage to buildings.

Abstract: In the immediate aftermath of an earthquake, quick estimation of damage to city structures can facilitate prompt, effective post-disaster measures. Physics-based urban earthquake simulations, using measured ground motions as input, are a possible means of obtaining reasonable estimates. The difficulty of such estimation lies in carrying out the simulation and arriving at a thorough understanding of large-scale time series results in a limited amount of time. We developed an estimation system based on fast urban earthquake disaster simulation, together with an interactive visualization method suitable for GPU workstations. Using this system, an urban area with more than 100,000 structures can be analyzed within an hour and visualized interactively.

Abstract: To improve the accuracy of inversion analysis of earthquake fault slip distribution, we performed several hundred analyses using a 10^8-degree-of-freedom finite element (FE) model of the crustal structure. We developed a meshing method and an efficient computational method for these large FE models. We applied the model to the inversion 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.