Seismologists rely on foreshocks as an indicator of when a large earthquake will occur because foreshocks precede all earthquakes and ample seismograph data has been collected on foreshocks.

Question

Quizplus · Accepted Answer

Foreshocks do precede some earthquakes, but not all significant earthquakes have identifiable foreshocks, and predicting the exact timing of an earthquake based on foreshocks remains highly uncertain.

Seismologists Rely on Foreshocks as an Indicator of When a Large