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 find the epicenter, geologists first determine the distance from a seismograph station to the epicenter by measuring the time difference between P - wave and S - wave arrivals. Then, they draw circles (with radius equal to this distance) around at least three seismograph stations. The intersection of these circles is the epicenter.

• Option 1: At least three seismographs are needed, not one.
• Option 2: Measuring the P - S wave arrival difference gives the distance from a station to the epicenter, which is a key step in the process of finding the epicenter.
• Option 3: The circles are drawn around the seismograph stations (not the epicenter) with radius as the distance to the epicenter.
• Option 4: Obtaining intensity information is for measuring earthquake strength, not finding the epicenter.

Answer:

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