A flurry of small earthquake activity within the last couple of days around Hawaii’s submarine volcano, the Loihi Seamount, has been reported by the the U.S. Geological Survey’s Hawaiian Volcano Observatory.
From midnight Sunday to midafternoon Monday, HVO detected 40 to 50 earthquakes of about 3.0 magnitude in the last 36 to 40 hours. “Nothing alarming yet, but definitely an uptick” said Tina Neal, HVO scientist in charge.
HVO’s network of seismometers on Hawaii island are able to detect the earthquakes, but most of the instruments are to the north or northwest and are “looking from one direction” at Loihi, located to the southeast of Pahala.
Despite the lack of monitoring instruments at Loihi, “there is no question what we’re seeing right now,” Neal said. The earthquakes are miles deep, some at depths of 7 miles.
Loihi, which rises to 3,100 feet below the ocean’s surface and lies 19 miles off the southeast coast of the Big Island, generates frequent earthquake swarms, the USGS says.
The last time a notable series of earthquakes occurred for a few weeks was in 1996 when 4,000 earthquakes were counted in the vicinity, with quite a few over magnitude 4.0. But nothing destructive occurred.
“I don’t think people should be worried about this,” Neal said, since they are “so far below the surface and the likelihood of them doing something destructive is very small,” and no significant tsunamis are expected to be generated.
Should anything significant occur, HVO will notify the public.
Scientists also are closely monitoring Mauna Loa, which is at advisory level due to 74 small earthquakes recorded at its summit at shallow depths in the week prior to Thursday.
There also is a steady increase in inflation at the summit, which reflects the amount of magma accumulating in its shallow reservoir.
But “there’s no sign it will be erupting anytime soon,” Neal said.
HVO also recently replaced a broken old gas sensor at Mauna Loa’s summit crater with an upgraded one which detects carbon dioxide, sulfur dioxide and hydrogen sulfide levels as well as temperature.