Editing Seismogram (section)

== Reading ==
Seismograms are read from left to right.

Time marks show when the earthquake occurred. Time is shown by half-hour (thirty-minute) units. Each rotation of the seismograph drum is thirty minutes. Therefore, on seismograms, each line measures thirty minutes. This is a more efficient way to read a seismogram. Secondly, there are the minute-marks. A minute mark looks like a hyphen "-" between each minute. Minute marks count minutes on seismograms. From left to right, each mark stands for a minute.

Each [[seismic wave]] looks different.  The [[P wave]] is the first wave that is bigger than the other waves (the [[microseisms]]). Because P waves are the fastest seismic waves, they will usually be the first ones that the seismograph records. The next set of seismic waves on the seismogram will be the [[S wave]]s. These are usually bigger than the P waves, and have higher frequency. Look for a dramatic change in frequency for a different type of wave.