This drum recorder was once part of a worldwide seismic network established in the early 1960’s to monitor underground nuclear weapons tests and earthquakes. Each drum records shaking of the ground- as it is happening- at one of the three locations indicated. The motions recorded on the drum are actual ground motions magnified several tens of thousands of times. Modern instruments can detect movements as small as one micron, or a millionth of a meter.
The big screen shows where earthquakes have happened today, yesterday, over the past two weeks and over the past five years. The small screen, updated every ten minutes, lists the most recent earthquakes shown on the map. Geologists determine the exact location of an earthquake by noting how long it takes the shock wave to travel to several different seismic stations.
Topic: Earth Science
Keywords: Earthquake magnitude--Measurement, Earthquakes, Seismology--Instruments