Above is a sample seismogram. Everything within the rectangle is what you could expect to see on a real seismogram -- the marks outside the rectangle note time intervals. As labelled, time on this record goes from left to right, meaning the left side of the seismogram was recorded before the right side.
Move the mouse over the seismogram to see more labels. Now you should be able to see that this record covers a little more than 30 seconds of time. A time tick is drawn exactly at the start of each minute, so we only see one on this record. About seven seconds after this tick, the recording line, or trace, moves down, then up, and so on in a somewhat chaotic manner, though always roughly centered on the original "quiet" level (a horizontal line evenly dividing the rectangle, in this case). This section of the seismogram is a waveform, the expression of ground motion as recorded by this instrument.
Click on the image to zoom out. The segment of the seismogram we were just studying is outlined in orange-red. Since this view shows you almost three minutes of the seismogram, you can now see two other tick marks (they are thinner because the time-scale is compressed) -- one occurs within the waveform recorded, the other happens near its end. You can now see that the motion recorded by the instrument eventually decays, and the trace becomes "quiet", like it was before the earthquake started. You can move the mouse off of the image to see it unlabelled, or click to zoom back in.Return to the main text