What is "seismographs"

Usage examples of "seismographs".

A new map, a cartology of Geiger counters, seismographs, radiosondes and gauges.

In those tense seconds it was as if he were endowed with a front seat at the dropping of a bigger and better atom-bomb with people in the back seats watching seismographs a thousand miles away.

A twelve-year-old boy, mounted on his first airors, was in position to strike the missile, but he blew it, punching too much power and overshooting, and screens all over the planet watched the missile fall the last few thousand feet until it was below horizon for all but the screens in the greater Dallas area and then seismographs registered the hit.