Q: Given a scientific passage and an answer, generate a question for the given answer.
Passage: Seismograms record earthquake strength. Scientists can use them to determine the distance to an earthquake. Using at least three seismograms, they can locate the earthquake's epicenter. Scientists measure earthquake intensity in several ways. So far no one has found a way to predict earthquakes. Answer: seismogram
A:
Scientists can use what tool to determine an earthquake's strength?