Chaine des Cascades , Etats-Unis : Dozens of quakes were detected .

Chaine des Cascades , Etats-Unis : Dozens of quakes were detected .

Current Volcano Alert Level: NORMAL
Current Aviation Color Code: GREEN

Activity Update: All volcanoes in the Cascade Range of Oregon and Washington are at normal background levels of seismicity. These include Mount Baker, Glacier Peak, Mount Rainier, Mount St. Helens, and Mount Adams in Washington State; and Mount Hood, Mount Jefferson, Three Sisters, Newberry, and Crater Lake in Oregon.

Recent observations: The swarm of small earthquakes that began last week near Gilcrest, Oregon (about 20 miles west-southwest of Newberry volcano) continued into this week but at reduced seismicity rates. Data from two new seismometers installed last weekend by CVO staff in the epicentral area have permitted more accurate earthquake locations and analysis. Dozens of quakes were detected, with the largest M = 3.0. Using data from the new seismometers, most events locate between 7 and 8 km depth. Epicenters are located in an area with numerous volcanoes younger than 1 million years (youngest is roughly 5000 years old) as well as many mapped faults. Similar swarms occurred in this area in 2001 and 2012, persisted for 2-3 months, then died away. Our interpretation at this point is that the swarm is most likely tectonic in origin. This past week CVO crews positioned bedrock benchmarks positioned for short-term GPS setups, as a means to measure ground deformation. For more information on the swarm see http://pnsn.org/blog/2015/10/23/unusual-earthquake-swarm-south-of-bend-or. A few earthquakes were also detected under Mount Rainier, Mount St. Helens and near Newberry this week, but all are considered to be normal background activity.

Heavy rain in connection with the season first atmospheric river (Pineapple Express) is forecast for today and tomorrow(10/30-31). Heaviest accumulations are expected in the Washington Cascades in the vicinity of Mount Rainier (about 12 inches), with the southern Washington and northern Oregon Cascades expected to receive 4 to 8 and possibly as much as 12 inches of rain. Minor to locally serious flooding, bank erosion, and some debris flows may occur along rivers draining Washington and northern Oregon volcanoes.

November 04, 2015. Chaine des Cascades , Etats-Unis :

Source : CVO

Photo : wikispace

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