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Foreshock

By Earthquake Hazards Program 2021 (approx.)
Seismic record with red, blue, and black waves. The largest seismic wave is labelled "Main shock," the second largest is labelled "Aftershock," and the third largest is labelled "foreshock.""
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Detailed Description

Small foreshocks on a seismic record. Foreshocks are relatively smaller earthquakes that precede the largest earthquake in a series, which is termed the mainshock. Not all mainshocks have foreshocks.

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