In so-called 'earthquake swarms', numerous earthquakes occur locally over an extended period without a clear sequence of foreshocks, main quakes and aftershocks. Earthquake swarms are a typical feature of seismic activity in Switzerland, and the Swiss Seismological Service (SED) registers several of them every year. Swarms usually end after a few weeks or months. Only seldom does the strength and number of earthquakes increase over time. How an earthquake swarm develops over time is just as difficult to predict as earthquakes are in general (see the question "Can earthquakes be predicted?").
Learn more
