Seismic noise of frequencies >1 Hz includes noise that is strongly related to human activities. Reduction in seismic noise during the COVID-19 pandemic has been observed worldwide as restrictions were imposed on numerous human activities to control outbreaks of the virus. In this context, we studied the effect of reduced anthropogenic activities during COVID-19 on the noise levels in the Tokyo metropolitan area, Japan, considering seasonal variation. A significant reduction in noise was observed during the emergency, including that of frequencies >20 Hz, which was associated with school activities. After lifting the state of emergency, noise reverted to previous levels immediately for weekdays, but gradually for Sunday. This was likely because economic activities instantly resumed post-emergency on weekdays; however, most people still continued to avoid non-essential outings on Sunday. We also observed seasonal variation related to school holidays, energy consumption, and industrial activity. Noise levels in the frequency range of 1–5 Hz were found to be related to construction activity, which increased in winter and gradually decreased from 2017. Our findings demonstrate that seismic noise can be used to monitor economic activities and movement of people at a local scale.

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Joint Program for Sustainable Resources Engineering was adopted as a Special Expenditure Project by the Ministry of Education, Culture, Sports, Science and Technology in Japan. In this project, in order to cultivate human resources who can contribute to Japan's resource strategies, Education and Research Departments of Resources Engineering at Kyushu University and Hokkaido University aim to jointly establish a new collaborative education program in 2017. This is the first of its kind in the resources engineering area among universities in Japan. One of the pillar of this program is "International Field Practice". For working actively and globally in the field of sustainable resources engineering, one need to (1) acquire internationally accepted knowledge and techniques in the fields, (2) be capable of utilizing the knowledge and techniques practically, and (3) understand cultures in foreign countries as well as global trends in the field. In this exercise, students work on an internship or conduct a field research in a foreign country in the field of sustainable resources engineering. Through this exercise, students learn how to develop their leadership and adaptability in the world, and to communicate scientifically and technically in English presentation, discussion, and writing. This paper describes the overview of this program and the International Filed Exercise 2017 conducted in Czech Republic.

Seismic ambient noise with frequencies > 1 Hz includes noise related to human activities. A reduction in seismic noise during the COVID-19 pandemic has been observed worldwide, as restrictions were imposed to control outbreaks of the SARS-CoV-2 virus. In this context, we studied the effect of changes in anthropogenic activities during COVID-19 on the seismic noise levels in the Tokyo metropolitan area, Japan, considering time of day, day of the week, and seasonal changes. The results showed the largest reduction in noise levels during the first state of emergency under most conditions. After the first state of emergency was lifted, the daytime noise reverted to previous levels immediately on weekdays and gradually on Sundays. This was likely because economic activities instantly resumed, while non-essential outings on Sundays were still mostly avoided. Furthermore, the daytime noise level on Sundays was strongly reduced regardless of changes on weekdays after the second state of emergency, which restricted activities mainly at night. Sunday noise levels gradually increased from the middle of the second state of emergency, suggesting a gradual reduction in public concern about COVID-19 following a decrease in the number of infections. Our findings demonstrate that seismic noise can be used to monitor social activities.

<p>To reveal the seismic velocity structure and anisotropy in potential geothermal fields, Kenya, we analyzed ambient noise data from nine vertical components of broadband seismometer stations. Our analysis is based on the cross-correlation of ambient noise data by extracting phase velocity dispersion curves via the zero-crossing method and then applying surface-wave inversion to estimate S-wave velocity structures. The results for both phase velocity and S-wave velocity structures show a clear velocity contrast in volcanic systems (i.e., Korosi-Paka-Silali) in the Kenyan Great Rift (KGR). The phase velocity structure (i.e., 1400 - 2200 km/s) significantly drops in the Silali trachytic shield volcano and the Pleistocene Paka shield volcano. Such velocity contrasts are also observed where they are parallel and perpendicular to the geological structure of the KGR. Most decreasing seismic velocities are normal to abundant faults and fractures in the inner trough of the KGR. This direction is aligned with local extension direction, linked to divergent plate boundaries. The resulting S-wave velocity structures further disclose the anomaly features that can indicate permeable or non-permeable layers. Permeable layers are extensively existing that can provide potential geothermal fluid accumulations. Most potential areas are below the rift floor between the Paka and Silali volcanoes, involved in intense faulting/fractures and young porous rocks (i.e., intercalated pyroclastic, trachyte, and basalt lavas). The lithocap zones are mostly less than 1 km. The magma heat sources are most likely deeper than 3 km at Paka and 4 km at Silali. Therefore, geothermal reservoirs can be relatively interconnected due to shallow magma-volcanic systems, existing groundwater, porous volcanic rocks (i.e., pumice) and intensive fractures controlled by main graben faults in the KGR, regardless of impermeable volcanic rocks or (ore) mineralization in this study area. This work was supported by Leading Enhanced Notable Geothermal Optimization (LENGO) of SATREPS (JICA-JST), Japan.</p><p>Keywords: ambient noise, S-wave velocity, seismic anisotropy, shallow magma-reservoir systems, rifting and volcanism</p>