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.""](https://d9-wret.s3.us-west-2.amazonaws.com/assets/palladium/production/s3fs-public/styles/full_width/public/media/images/foreshock.gif?itok=hBnqwsss)
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.