Mount St. Helens earthquake record during times of magma recharge. The top plot is the number of located earthquakes per week in the Pacific Northwest Seismic Network catalog. The bottom plot shows the earthquake depths with time. Earthquakes are plotted as circles with the size of the circle corresponding to the magnitude of the earthquake (see legend). Both plots show the time period from 1987 to September 2004, and 2008 to May 4, 2016. The 2004 to 2008 eruption at Mount St. Helens has been removed from this record for simplicity. (USGS)