Final answer:
Seismographs measure the arrival times of seismic waves to determine the distance to an earthquake's epicenter. However, the precision of this measurement depends on the precision of the seismograph and the propagation speeds of the waves. When using seismic waves from underground detonations, the uncertainty in determining the distance is increased.
Step-by-step explanation:
Seismographs measure the arrival times of seismic waves to determine the distance of the earthquake's epicenter. They compare the arrival times of S-waves and P-waves, which travel at different speeds. By analyzing the time difference between the arrival of these waves, the distance to the source of the earthquake can be determined. However, the precision of this measurement depends on the precision of the seismograph and the propagation speeds of the waves.
In the case of seismic waves from underground detonations of nuclear bombs, determining the distance to the test site and detecting violations of test bans can be challenging. This is because the precision of seismographs is limited, and any uncertainty in the propagation speeds of S-waves and P-waves further increases the uncertainty in determining the distance. Therefore, while seismic waves can be used for detection, there are limits to their precision.