Development of Semi-Real-Time Tsunami Monitoring and Calculation System on Ocean-Bottom Stations off the Kii Peninsula, Southwest Japan

We developed a semi-real-time calculation and data monitoring system that measures pressure perturbations at ocean-bottom pressure-gauge stations deployed off the Kii peninsula in southwest Japan in order to identify tsunami signals associated with earthquakes. The system automatically calculates geodetic deformations and tsunami propagation immediately after getting seismic source information on hypocenter, magnitude, and mechanism. The calculation results for transoceanic tsunamis can be available in approximately 20 s after getting source information to output waveform data by executing the optimized parallel calculation code on our computer server SGI UV2000 with a 32-core processor unit. The system also provides tide-removed and filtered waveform data at ocean-bottom stations, enabling the calculation results to be compared with actual tsunami arrivals. System operations began in July 2015 and have been applied to tsunamigenic earthquakes in the Pacific Ocean. The system is effective in identifying tsunami signals and automatically predicting tsunami propagation in offshore areas, which may be useful for further data analyses on tsunami propagation.

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