It was a man on duty in the control room, overhead, reporting that two Emergences had just been detected at twenty light-minutes due north of the planet.
"Space Viking"
Henry Beam Piper
Three minutes later, the control tower picked up two Emergences at a light-second and a half, a thousand or so miles apart.
"Space Viking"
Henry Beam Piper
Again, he remarks, the observed Emergences at places near the epicentre indicate that the vertical section of the seismic focus was either more or less curved, or more probably a surface inclined towards the south-east.
"A Study of Recent Earthquakes"
Charles Davison