A seismogram is a written seismographic record obtained from ground motions as a result of earthquakes or explosions in the form of seismic waves. Seismic waves on a seismogram look like wiggly lines that are spread across the width of the paper.
Most seismic waves are so small they cannot be felt and are known as tiny microseisms. They are readings caused by commonplace disturbances to the seismograph, such as automobile traffic, wind and ocean waves hitting a beach. Evenly spaced marks or dots may appear, which indicate the turning of the seismograph drum per minute. The amount of space between these markings depends on the type of seismograph being used.