Earthquake: Foreshock—Mainshock—Aftershock

6min 32s Novice Spanish

There is often confusion surrounding the terminology of earthquakes. Large earthquakes are usually followed by hundreds and even thousands of smaller earthquakes, called aftershocks. In some earthquake sequences, a smaller earthquake called a “foreshock”, precedes the mainshock. Although seismologists have carefully analyzed foreshock/mainshock pairs of earthquakes, and earthquake triggering in general, there are no special characteristics of a foreshock that let us know it is a foreshock until the mainshock occurs. Rate of aftershocks was first studied in detail by Fusakichi Omori, Chairman of Seismology at Imperial University of Tokyo; one of the most important figures in the history of seismology.

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