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ALASKA VOLCANO OBSERVATORY INFORMATION STATEMENT
U.S. Geological Survey
Tuesday, June 30, 2020, 1:43 PM AKDT (Tuesday, June 30, 2020, 21:43 UTC)
53°53'24" N 166°55'30" W,
Summit Elevation 5906 ft (1800 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW
Over the past two weeks, there has been increased earthquake activity at Makushin Volcano. The activity started on June 15 with a magnitude 4.2 earthquake, followed over the next 24 hours by several additional significant earthquakes ranging in magnitude from 3.1 to 4.1. These larger earthquakes have been accompanied by hundreds of smaller earthquakes located by AVO that are continuing up to the present time. The rate of occurrence and size of the earthquakes initially declined for about a week following the magnitude 4.2 earthquake. However, since June 24, the rate and size of the earthquakes has fluctuated with the most recent increase associated with two earthquakes of magnitude 3.0 and 3.8 that occurred at 4:53 PM and 6:02 PM on June 28. All of the earthquakes are clustered about 10 km (6 miles) east of the summit of the volcano at a depth of about 8 km (5 miles). The largest earthquakes have been felt strongly by residents of Unalaska.
The exact cause of this increased earthquake activity, in terms of possible volcanic or tectonic processes, is uncertain at this time. The earthquakes may be related to the movement of magma beneath the east side of Makushin Volcano, interactions between an earthquake fault and the nearby geothermal field, the activation of more than one fault in this area, or a combination of these scenarios. Because of the distance and depth of the locations of the earthquakes from the summit of Makushin Volcano, and the absence of other forms of volcanic unrest such as increased steaming, gas emission, or ground deformation, there is no indication that the present earthquake sequence will necessarily lead to a volcanic eruption. In response to this earthquake activity, AVO raised the Aviation Color Code to Yellow on June 15 and plans to continue close monitoring of seismic activity, ground deformation, and gas emissions at Makushin Volcano over the coming weeks and will provide additional information as it becomes available
Makushin Volcano is located on northern Unalaska Island in the eastern Aleutian Islands. Makushin is a broad, ice-capped stratovolcano that rises to an elevation of 6680 feet. The summit caldera, 3 km diameter, is the site of frequent steam and minor ash eruptions; however, no large eruptions have occurred in this century. Makushin is monitored by a network of seismic stations, web camera, GPS, satellite images, and regional infrasound and lightning detection data. The community of Unalaska and port of Dutch Harbor are located 25 km (16 miles) east of Makushin volcano.
OTHER ALASKA VOLCANOES
Information on all Alaska volcanoes is available at : http://www.avo.alaska.edu.
For definitions of Aviation Color Codes and Volcano Alert Levels, see: http://www.avo.alaska.edu/color_codes.php
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Michelle Coombs, Scientist-in-Charge, USGS
email@example.com (907) 786-7497
David Fee, Coordinating Scientist, UAFGI
firstname.lastname@example.org (907) 322-4085
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.