Takeshi Nakamura, a technical researcher at the Japan Agency for Marine-Earth Science and Technology, collaborated with Okayama University, Tokyo Institute of Technology, and Fukui University to measure the seafloor strong motion meter data of the earthquake and tsunami observation and monitoring system "DONET" and analyze it with the spacon "K computer". We discovered that long-period ground motions are occurring over a wide area of the deep sea floor due to large-scale earthquakes.
In this study, we analyzed long-period ground motion data at the time of a medium-scale earthquake with the epicenter of Awaji Island, which occurred on April 2013, 4, captured by "DONET".It was found that the tremor of a general earthquake becomes weaker when it is far from the epicenter, while the tremor is amplified even though the observation points such as off Mie prefecture are far from the epicenter.It was also found that the shaking lasted for a very long time compared to land.Furthermore, analysis using the supercomputer "K computer" revealed that the cause of such shaking was the sedimentary layer on the seafloor.These facts have been pointed out by indirect data, but they are directly proved in this study.
This result will be a new finding for identifying the epicenter and scale immediately after the earthquake.In addition, the Group will continue to investigate in more detail the process of long-period ground motion and the structure of the seafloor sedimentary layer for future disaster prevention and mitigation.