Small quakes at Mount Edgecumbe likely due to magma movement

While earthquake activity around Mount Edgecumbe has declined following a series of small quakes last month, further investigation by the Alaska Volcano Observatory shows that the area around the mountain has been steadily deforming since 2018, likely due to the movement of magma.

The observatory said in an online post: “The recent (earthquake) swarm inspired an in-depth analysis of the last 7.5 years of ground deformation detectable with radar satellite data.” That analysis revealed a broad area, almost 11 miles in diameter, “of surface uplift” just east of Mount Edgecumbe.

“The coincidence of earthquakes and ground deformation in time and location suggests that these signals are likely due to the movement of magma beneath Mount Edgecumbe,” rather than tectonic activity.

Since 2018, the land immediately surrounding Mount Edgecumbe has risen by almost 3.5 inches annually, for a cumulative deformation of 10.6 inches, the observatory said on its website.

Other parts of southern Kruzof Island where Mount Edgecumbe is located have experienced lesser degrees of deformation, the observatory noted.

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

The quakes and uplifting terrain are not cause for alarm, said Dave Schneider, a USGS research geophysicist at the observatory. His Anchorage-based team will come to Sitka this month to investigate more thoroughly and present information to the public.

In the short term, Schneider wants to place sensors and gather additional data.

The recent series of small earthquakes beneath Mount Edgecumbe was detected by the Alaska Earthquake Center in Anchorage.

After a spike in seismic activity last month, quake activity beneath the mountain has declined.


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