A New View On What's Shaking on the Cascade Volcanoes

February 26, 2014

by Jon Connolly

We have added a new interactive graphic to the PNSN home and volcano page that provides a quick summary of the latest Cascade volcanic seismicity. This graphic replaces a table view of the same data. We have strived to make the PNSN landing page a quick summary view of immediate information that allows a user to drill down for more info if desired.  The table view for recent volcanic seismicity was a bit clumsy and fell short of this goal.


The  timeline shows the earthquake distribution in a moving 30 day window, which is recalculated every 1-5 minutes. The volcanoes are ordered by most to least seismically active. Volcanoes without recent seismicity are listed as links at the bottom.  Each recently seismic volcano has a mouse hover state that will display the earthquake count for the last 30 days.  If more information is desired for any of the volcanoes, a user can click on the link to go to the appropriate volcano page. The volcano maps show the last 20 earthquakes near the volcano.  For seismically busy volcanoes, such as Mount St. Helens and Mount Rainier, this spans a very short time (weeks to months), but for quieter volcanoes such as Glacier Peak, this spans the entire PNSN catalog (1969-Present).

For the purpose of this graphic an earthquake is considered volcanic if it occurs within 10km of the summit of the volcano. For the Three Sisters, the radius is calculated from a centroid between the three peaks. The 10km radius is fairly arbitrary but serves the motivation of this graphic: How seismic has each Cascade volcano been lately?