how many detectable earthquakes each year
Most quakes are unnoticeable by people on the surfacein fact, thousands of quakes occur every day around the globe, most of them too weak to be felt. Every year, scientific instruments detect about 500,000 quakes worldwide. People feel only a small fraction of those. On average, a magnitude 8 quake happens every year somewhere on Earth. But severe earthquakes that cause widespread destruction happen on average once every five years. These great quakes can destroy cities, burst dams, trigger volcanic eruptions, and set off landslides and giant sea waves.