The ongoing earthquake swarm in Yellowstone National Park, central US, which houses a supervolcano has reached 878 events recorded from June 12 to June 26. The largest magnitude event measured 4.4 on the Richter scale, while over 500 were in the magnitude 0 range, scientists said. Yellowstone sees around 1,500-2,000 earthquakes per year with 50% in the form of swarms.