Question

which is one step that geologists use to find the epicenter of an earthquake?
○ they look at data from at least one seismograph.
○ they measure the difference between arrival of p waves and s waves.
○ they draw circles around the epicenter from three locations.
○ they obtain information about the intensity of earthquakes from seismographs.

Explanation:

To locate an earthquake's epicenter, geologists need data from at least 3 seismographs. A key intermediate step is measuring the time difference between the arrival of faster P-waves and slower S-waves at a seismograph station; this difference is used to calculate the distance from the station to the epicenter.

• Option A is incorrect because at least 3 seismographs are needed, not one.
• Option C is incorrect because circles are drawn around seismograph stations (not the epicenter) using calculated distances; their intersection is the epicenter.
• Option D is incorrect because seismographs measure wave arrival times, not earthquake intensity directly (intensity is assessed via damage reports).

Answer:

B. They measure the difference between arrival of P waves and S waves.