How Seismographs Measure Earthquakes: Science Fun Facts
How do scientists measure seismological events in the earth? Read more to learn about the tools they use to measure and locate earthquakes and other movements in the earth.
Seismometers are scientific instruments that collect data on earthquakes, volcanic eruptions, and explosions. These instruments are important tools used to measure and locate these geologic events as well as create a map of internal structures in the earth. The seismometer works by measuring movements in the ground and can detect the smallest of ground movements. While there are many different kinds of seismometers, they all function with the same basic principle.
A supporting structure is anchored to the ground and supports a free mass that is used to measure the intensity of an earthquake or other seismic event. The intensity of the seismic event is recorded either on paper or electronically. Generally, a seismometer can only measure waves from a single direction, so multiple instruments are needed in order to record waves from more than one direction.
There are four main types of waves recorded on a seismometer. Two of these body waves (P and S waves) travel deeper in the earth, and the other two travel at the surface (L waves). The P (primary) wave is the first to be recorded on a seismograph and can travel at 6 kilometers per second. The S (secondary) wave is similar to the P wave in its pattern but follows after it. In order to locate an earthquake, scientists can calculate the time interval between P and S wave arrivals on the seismograph stations.