  Human movement is used as an indicator of human activity in modern society.
The velocity of moving humans is calculated based on position information
obtained from mobile phones. The level of human activity, as recorded by
velocity, varies throughout the day. Therefore, velocity can be used to
identify the intervals of highest and lowest activity. More specifically, we
obtained mobile-phone GPS data from the people around Shibuya station in Tokyo,
which has the highest population density in Japan. From these data, we observe
that velocity tends to consistently increase with the changes in social
activities. For example, during the earthquake in Kumamoto Prefecture in April
2016, the activity on that day was much lower than usual. In this research, we
focus on natural disasters such as earthquakes owing to their significant
effects on human activities in developed countries like Japan. In the event of
a natural disaster in another developed country, considering the change in
human behavior at the time of the disaster (e.g., the 2016 Kumamoto Great
Earthquake) from the viewpoint of velocity allows us to improve our planning
for mitigation measures. Thus, we analyze the changes in human activity through
velocity calculations in Shibuya, Tokyo, and compare times of disasters with
normal times.
