Volcano activity of April 12, 2013 – Update, Newberry volcano seismicity (Oregon, USA)

Last update: April 13, 2013 at 3:02 am by By Richard Wilson and Armand Vervaeck

Update Newberry volcano

Interesting press release from CVO this evening.  While they’re playing this down, it is interesting that there are (and have been) many more earthquakes than they mention in the report (for days now!)!  The events plot beneath the most recent vent area,…not where geothermal exploration this past year had triggered earlier activity on the western flank of the volcano.  I had been watching these events, but obviously not closely enough!!!  I’m sure the deep low-frequency event within the shallower activity got their attention.  This is a rhyolitic volcano (so there are few analogs to precursory activity) and the seismicity at Chaiten and more recently at Cordon Caulle began at around 8 km depth!!

Maybe nothing,…maybe something!!!  Definitely the most interesting seismicity in the Cascades for a long while!!!

Earthquakes at Newberry, April 08-12 – 
April 12, 2013
Between 04/08 – 04/12, five earthquakes were located within or along the margins of the Newberry caldera by the Pacific Northwest Seismic Network (PNSN, http://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.

Newberry earthquakes, 2011 – 2013
Map showing earthquakes located within the Newberry caldera from 2011 – 2013. Earthquakes from April 08-12, 2013, are colored orange or red (for April 12 events).

Although these five events are nothing to get excited about, they are noteworthy because only six other earthquakes have been located within or along the margins of the Newberry caldera since the Newberry seismic network was expanded from one to nine seismic stations in the summer of 2011 (none of these events would have been detected prior to 2011). In addition, the 04/11 event is the first low-frequency event ever recorded in the Newberry area. Low-frequency events are not unusual at volcanoes, and when observed are commonly thought to reflect movement of fluid (water, gas, or other) through cracks. Given that there are active hot springs within the caldera, the occasional occurrence of such events should not be surprising. An unusual feature of this low-frequency event is its depth (8 km). Since the 1980s, such “deep low-frequency events” have been seen intermittently at Mount Baker (31), Glacier Peak (9), Mount Rainier (9), and Mount St. Helens (9). At these other volcanoes the deep low-frequency events occur as part of background seismicity and have not been associated with eruptions or unrest at the surface (for more information about these type of events in the Cascades, see Nichols et al. (2011)**). Although intriguing from a volcanological perspective, these events are again nothing to get excited about.
** Nichols, M. L., S. D. Malone, S. C. Moran, W. A. Thelen, and J. E. Vidale (2011), Deep long-period earthquakes beneath Washington and Oregon volcanoes, Journal of Volcanology and Geothermal Research, 200(3-4), 116-128.

from:    http://earthquake-report.com/2013/04/12/volcano-activity-of-april-12-2013/