What do earthquakes represent?

In the story, earthquakes symbolize widespread tragedy and societal panic. The story takes place one month after the Kobe earthquake of 1995, and Frog enlists Katagiri to prevent an earthquake from striking Tokyo. Frog states that Katagiri’s courage is necessary for the success of the mission, and thus the story seems to thematically assert the importance of communal courage in the wake of tragedies.