Seismic measurements
A typical «event»
Stromboli volcano has been active for thousands of years. Normally it erupts several times per hour. In each eruption red-hot pyroclastics and clouds of ash are thrown dozens of metres into the air:
These eruptions are recorded by our seismic station. We call the corresponding seismic signal an «event»:
Sometimes these events follow each other very rapidly. In this example there were three in just one minute: