"Between 8-12 April, five earthquakes were located within or along the margins of the Newberry caldera by the Pacific Northwest Seismic Network (PNSN, www.pnsn.org). The first two occurred at 04:19 & 04:20 PDT on 04/08 and were followed over the next 20 minutes by eight smaller (and therefore unlocatable) earthquakes.
"Three days later at 5:01 PDT a "low-frequency event", so-called because it lacks higher-frequency waves that are commonly observed in regular earthquakes, occurred at a depth of ~8 km. Finally on 04/12 two additional earthquakes occurred at 02:28 and 04:06 PDT. The largest of these five events was a M 1.2. These five events appear as orange or red (two most recent) circles in the below map-view plot. [less]