Mauna Loa volcano making threatening noises

KAILUA-KONA, Hawaii — Earthquakes have been rumbling more frequently deep beneath Mauna Loa, suggesting that the world’s largest volcano is getting ready to erupt for the first time in 20 years, scientists said.

“We don’t believe an eruption is right around the corner, but every day that goes by is one day closer to that event,” said Paul Okubo, a seismologist at the Hawaiian Volcano Observatory on the Big Island.

Mauna Loa erupted for three weeks in 1984, sending a 16-mile lava flow toward Hilo. Since then, the U.S. Geological Survey estimates that more than $2.3 billion has been invested in new construction along Mauna Loa’s slopes.

Since July, more than 350 earthquakes have been recorded far beneath the 13,677-foot-high Mauna Loa, said Don Swanson, scientist-in-charge at the observatory.

“Mauna Loa is grumbling, growling and getting ready to come out of its den,” he said.

The earthquakes have been what seismologists call “long period,” which means their signals gradually rise above the noise generated by usual seismic activity.

“Such a concentrated number of deep, long-period earthquakes from this part of Mauna Loa is unprecedented, at least in our modern earthquake catalog dating back to the 1960s,” Okubo said.