MAKUSHIN VOLCANO

A magnitude-6.4 earthquake hit about 25 miles east of Nikolski Tuesday morning, and was felt by residents in Nikolski, Unalaska, and Akutan. The earthquake hit just before 7:30 a.m.

It was a "reasonable size tectonic earthquake," according to Dave Schneider, a geophysicist with the Alaska Volcano Observatory. He said Aleutian Island residents can expect to feel some aftershocks.

"This is a pretty typical tectonic earthquake for the region," he said. "It's on a very seismically active part of the Aleutian arc, and there's nothing that jumps out as being unusual."

Scientists have downgraded the alert level at Makushin Volcano after a sustained pause in unrest. 

John Power, a geophysicist with the Alaska Volcano Observatory, said the seismicity has been steadily declining for months, following an earthquake sequence near the volcano that began in mid-June. 

A decades-long effort to bring geothermal power to Unalaska is finally moving forward. On Thursday, the city signed a 30-year power purchase agreement (PPA) with Ounalashka Corp./Chena Power, LLC for 30 megawatts of geothermal-produced electrical energy from nearby Makushin Volcano. Officials from the U.S. Department of Energy said that if it's successful, Unalaska would be the first community in the nation completely powered by geothermal energy. 

Over the past two weeks, there has been increased earthquake activity near Makushin Volcano. The activity started on June 15 with a magnitude 4.2 earthquake, followed by several additional significant earthquakes ranging in magnitude from 3.1 to 4.1 over the next 24 hours.

These larger earthquakes have been accompanied by over 850 smaller ones located by the Alaska Volcano Observatory since mid-June. 

More than half of the City of Unalaska's tsunami sirens aren't functioning, according to city officials.

The city tested its tsunami sirens, which were purchased in 1996, on Wednesday. Three out of seven worked. 

Following a number of earthquakes near Makushin Volcano earlier in the week — which prompted the Alaska Volcano Observatory to increase the volcano's alert level to "advisory" — local concern about Unalaska's emergency preparedness has been elevated.