Small swarm on SE flank of Newberry Volcano, November 14-15, 2013.
These earthquakes are the first to be located on the SE flank of Newberry since the Cascades Volcano Observatory added eight stations to the Newberry seismic network in 2011.
During November 14-15 the Pacific Northwest Seismic Network (PNSN, http://www.pnsn.org) located 12 earthquakes on the SE flank of Newberry Volcano, roughly 5-10 km from the center of the caldera. A roughly equivalent number of earthquakes were detected but were too small to be located. The largest event (M 2.0) occurred November 15 at 1110 UTC (0310 PST) with a depth of 3.9 km, and other events have depths generally < 6 km. The map shows the 12 events located by the PNSN as of 10:30 a.m. PST on November 15.
Swarms of small events such as this one could conceivably have gone undetected at Newberry before the 2011 upgrade, so swarms like this may be a normal part of background seismicity in the Newberry area. It often takes several years to fully understand the normal background seismicity level at individual volcanoes, which is why it is important to install seismic networks, as well as networks of other types of sensors, many years before any volcanic unrest begins. For those who are interested, here is a link to a recent USGS publication that details the type of monitoring networks which ideally should be in place at our most hazardous volcanoes well before any signs of unrest.