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.

 It has been confirmed that when a large-scale earthquake occurs, the shaking of the building is steadily amplified by long-period ground motion.Many examples have been reported on land in basins and plains, but simulation results only point out that similar things may be happening on the seafloor.Even if it is a tremor on the seabed, the tremor can reach the land.It has been pointed out that this may affect earthquake motion prediction such as Earthquake Early Warnings.In order to improve the quality of such forecasts, it is necessary to clarify the characteristics of long-period ground motions on the seafloor.The earthquake and tsunami observation and monitoring system "DONET" has been in operation since 2010 to analyze long-period ground motions on the seafloor around the Nankai Trough.

 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.

Okayama University

Promote the creation of an environment and system that can fly as a practitioner who can play an active role globally

A national university with 150 faculties, 10 graduate schools, and 8 research institutes, which is about 4 years old.Based on the results of advanced research activities, we can cultivate the ability of students to participate in "creation of knowledge" independently, and foster a rich humanity through close dialogues and discussions between students and faculty members. In a wide range of fields both domestically and internationally […]

Tokyo Institute of Technology

The pinnacle of science and engineering university that continues to produce science and engineering people with high aspirations and a Japanese spirit, mastering the knowledge that creates the times, refining their skills

Tokyo Institute of Technology was established as the Tokyo Institute of Technology in 1881 (Meiji 14), when modernization of industry was an urgent need.Since its establishment, it has continued to produce excellent research results with excellent science and engineering human resources, and is still at the top of Japan's science and engineering universities.Tokyo Institute of Technology requires not only a high degree of specialization but also liberal arts […]

Fukui University

Fostering excellent human resources who can play an active role as highly specialized professionals in the global society of the 21st century

The University of Fukui has a philosophy of "opening up the future of people and society through qualification", and as a center of science and culture, under high ethical standards, it is a world-class science and technology for people to live in good health. Promote education and research and develop human resources who can contribute to the region, country and international society.In the fields of education, medicine, and engineering, the ground […]

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