<p><strong>SF Fig. 7.3.</strong> A seismogram shows the data from a seismograph. Wave velocity is measured on the y axis, and time in seconds is measured on the x axis. P waves are recorded earlier than S waves, because they travel at a higher velocity.</p>

SF Fig. 7.3. A seismogram shows the data from a seismograph. Wave velocity is measured on the y axis, and time in seconds is measured on the x axis. P waves are recorded earlier than S waves, because they travel at a higher velocity.

Image courtesy of Crickett, Wikimedia Commons