Question

how many seismometers are needed to find the epicenter of an earthquake?
1
4
about 10 (depending on strength and location)
seismometers are not used to find the epicenter - only show us the strength

Explanation:

Three seismometers are needed to find the epicenter of an earthquake. By measuring the time - difference of arrival of seismic waves at each of the three seismometers, the distance from each seismometer to the epicenter can be calculated, and the intersection of the three circles (centered at the seismometers with radii equal to the calculated distances) gives the epicenter.

Answer:

B. 3