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Abstract:The tsunami generated by the 2011 Tohoku-Oki earthquake was the first time that the velocity fields of a tsunami were measured by using high-frequency oceanographic radar (HF radar) and since then, the development of HF radar systems for tsunami detection has progressed. Here, a real-time tsunami detection method was developed, based on virtual tsunami observation experiments proposed by Fuji et al. In the experiments, we used actual signals received in February 2014 by the Nagano Japan Radio Co., Ltd. radar system installed on the Mihama coast and simulated tsunami velocities induced by the Nankai Trough earthquake. The tsunami was detected based on the temporal change in the cross-correlation of radial velocities between two observation points. Performance of the method was statistically evaluated referring to Fuji and Hinata. Statistical analysis of the detection probability was performed using 590 scenarios. The maximum detection probability was 15% at 4 min after tsunami occurrence and increased to 80% at 7 min, which corresponds to 9 min before tsunami arrival at the coast. The 80% detection probability line located 3 km behind the tsunami wavefront proceeded to the coast as the tsunami propagated to the coast. To obtain a comprehensive understanding of the tsunami detection probability of the radar system, virtual tsunami observation experiments are required for other seasons in 2014, when the sea surface state was different from that in February, and for other earthquakes.

The 2011 Tohoku earthquake and tsunami caused the loss of 20,000 lives in Japan. According to the National Police Agency (2012), 90% of deaths in the Iwate, Miyagi, and Fukushima prefectures were due to drowning. On the other hand, this report also showed that the remaining 10% died from circumstances other than drowning, as suggested by the Japanese Society of Legal Medicine (2012). A new solution is needed to propose practical measures against a tsunami. In this paper, the authors suggest the science of human survival from disaster as one of the solutions and illustrate the research design implemented to build it. Constructing the science of human survival shall be important to mitigate human damages in future tsunami disasters.

In this paper, we report on how the prolonged COVID-19 pandemic affected children and adolescents' physical activity and mental health. Previous studies in PubMed revealed that only one of the 107 studies currently reported the impact of the prolonged. Therefore, a web-based questionnaire survey was conducted in Japan on February 10, 2022. A total of 236 adults (84 males and 152 females) responded to the electronic survey. Participants with children in the elementary school reported that their opportunities for exercise had decreased (100%), while 11% of participants with children in middle school or high school reported that they thought their opportunities had increased considerably. As for stress, 100% of participants with middle school or older children reported feeling it. In the KH Coder analysis of the free text, elementary school children seemed concerned about adjusting to life changes such as being silent about school lunches. On the other hand, junior high school and high school students were found to be adapting to the life changes caused by the COVID-19 but were also facing increased stress and new infection risks. It is necessary to divide the support for children and adolescents in prolonged COVID-19 pandemic according to their age.