Final answer:
To determine the location of an earthquake, at least three seismic stations are needed for accurate triangulation, using the arrival times of seismic waves which travel at known speeds.
Step-by-step explanation:
To triangulate the location of an earthquake, a minimum of three seismic stations are required. This process is known as triangulation, and it involves using the differences in arrival times of seismic waves at each station to determine the precise origin, or epicenter, of the earthquake. Triangulation ensures that the intersecting circles (representing the distance from each station to the earthquake based on the seismic waves' speeds and arrival times) pinpoint an exact location. Seismographs with a precision of 0.100 seconds comparing the arrival times of S-waves and P-waves, can determine the distance to the epicenter when the waves' speeds are known.
In the example provided, if S- and P-waves travel at 4.00 km/s and 7.20 km/s respectively, the precision of locating an earthquake can be affected by the certainty of these wave speeds and the timing accuracy. This precision is also critical for monitoring underground detonations of nuclear bombs and ensuring compliance with test bans.