Seismogram

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Bold textHello yall A seismogram is a graph output by a seismograph. It is a record of the ground motion at a measuring station. The energy measured in a seismogram may result from an earthquake or from some other source, such as an explosion.

Because P-waves travel through the earth faster than other types of waves, the P-wave is the first arrival of energy from an earthquake or other seismic source to be recorded. The next direct arrivals are the S-waves, and, finally, surface waves. Many reflected and refracted arrivals are typically recorded as well.

A set of seismograms for an earthquake from the USGS (click to see large version)

Historically, seismograms were recorded on paper attached to rotating drums. Some used pens on ordinary paper, while others used light beams to expose photosensitive paper. Today, practically all seismograms are recorded digitally to make analysis by computer easier. Some drum seismometers are still found, though, especially when used for public display.

[edit] External links

• An example seismogram
• REV, the Rapid Earthquake Viewer Seismograms recorded around the world from recent earthquakes (weeks old) as well as larger earthquakes from the past.

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