Mount Rainier 2.3 quake and swarm, September 20, 2009
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A swarm of small earthquakes started on the morning of September 20, 2009, at about 09:00 PDT beneath Mount Rainier. To date, the swarm has consisted of hundreds of earthquakes, most occurring on Sept. 20. Most locate at a depth of 2-3 km (1-2 miles) beneath the northeast flank of the volcanic edifice, centered ~1 km (0.5 miles) northeast of the summit. The largest event was a M 2.3 on Sept. 20. As of Sept. 23 swarm events continue, but at a greatly reduced rate since early on September 22. Seismic swarms are concentrations of earthquakes that typically are not initiated with a mainshock, and are common features at volcanoes. The vast majority of volcanic swarms are not associated with eruptive activity. Rainier itself has had several such swarms: in the past 7 years there have been similar days-long swarms in 2002, 2004, and 2007, two of which (2002 and 2004 )included M 3.2 earthquakes. The Sept. 20 swarm has produced the largest number of events of any swarm at Rainier since seismic monitoring began over two decades ago, so we will continue to closely monitor seismicity and other geophysical parameters at Rainier.
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CVOLC 2009
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CVOLC 2009 ----- Cascades Volcano Observatory Lunch Colloquium
CVOLC is BACK !!! --- "Brown-Bag" Lunch Talks at CVO
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