The distance between a seismic station and the earthquake epicenter in determined from the

Flying moons

Explanation:

The words that remind the reader that this is a story set in space are "flying moons." On Earth, we do not usually refer to our moon as "flying." However, even if we did, we can only see a single moon. Therefore, the presence of several moons indicates that the story must be taking place outside of Earth, in outer space.