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AVO/USGS Volcanic Activity Notice

Volcano: Semisopochnoi (VNUM #311060)

Current Volcano Alert Level: UNASSIGNED
Previous Volcano Alert Level: ADVISORY

Current Aviation Color Code: UNASSIGNED
Previous Aviation Color Code: YELLOW

Issued: Thursday, May 28, 2015, 1:52 PM AKDT (20150528/2152Z)
Source: Alaska Volcano Observatory
Notice Number: 2015/A3
Location: N 51 deg 55 min E 179 deg 35 min
Elevation: 2625 ft (800 m)
Area: Aleutians Alaska

Volcanic Activity Summary: A decline in seismicity over the last few months and no sign of activity in daily satellite images prompts AVO to downgrade Semisopochnoi volcano from Aviation Color Code YELLOW and Volcanic Alert Level ADVISORY to UNASSIGNED.

Following a brief seismic swarm in June and July, 2014, an increase in seismicity at Semisopochnoi seismic stations was recorded in January 2015. Numerous small earthquakes, most with magnitudes less than 1 over the next several months led AVO to include Semisopochnoi in the March 20, 2015 Weekly Update. On March 25, 2015, citing increased earthquake activity including brief periods of tremor, AVO raised the Aviation Color Code and Volcano Alert Level to YELLOW/ADVISORY. Over the next two months seismic levels have declined and no activity has been observed in daily satellite images or other remote sensing data.

AVO will continue to monitor Semisopochnoi seismic data and evaluate daily satellite images.

Recent Observations:
[Volcanic cloud height] Unknown
[Other volcanic cloud information] Unknown


Contacts: Chris Waythomas, Acting Scientist-in-Charge, USGS
chris@usgs.gov (907) 786-7497

Jeff Freymueller, Coordinating Scientist, UAFGI
jeff.freymueller@gi.alaska.edu (907) 322-4085



Next Notice: A new VAN will be issued if conditions change significantly or alert levels are modified. While a VAN is in effect, regularly scheduled updates are posted at http://www.avo.alaska.edu

The Alaska Volcano Observatory is a cooperative program of the U.S. Geological Survey, the University of Alaska Fairbanks Geophysical Institute, and the Alaska Division of Geological and Geophysical Surveys.

VOLCANO ALERT LEVELS
NORMAL
Volcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.
ADVISORY
Volcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.
WATCH
Volcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway but poses limited hazards.
WARNING
Hazardous eruption is imminent, underway, or suspected.
AVIATION COLOR CODES
GREEN
Volcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.
YELLOW
Volcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.
ORANGE
Volcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway with no or minor volcanic-ash emissions [ash-plume height specified, if possible].
RED
Eruption is imminent with significant emission of volcanic ash into the atmosphere likely OR eruption is underway or suspected with significant emission of volcanic ash into the atmosphere [ash-plume height specified, if possible].
Contact AVO Privacy Accessibility Information Quality FOIA
URL: www.avo.alaska.edu/activity/avoreport.php
Page modified: May 16, 2014 09:40
Contact Information: AVO Web Team

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