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HVO: Seismic activity below Loihi over weekend likely due to magma movement

Nina Wu
COURTESY USGS
                                A map of the earthquake swarm beneath Kamaʻehuakanaloa, or Loihi, a seamount south of Hawaii island.
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COURTESY USGS

A map of the earthquake swarm beneath Kamaʻehuakanaloa, or Loihi, a seamount south of Hawaii island.

The U.S. Geological Survey says increased seismic activity beneath the Loihi seamount over the weekend is likely due to magma movement, but says they are not likely to lead to an eruption.

USGS’s Hawaiian Volcano Observatory first detected the earthquake swarm beneath Kamaʻehuakanaloa, or Loihi, a seamount south of Hawaii island at about 2 a.m. Saturday. HVO said it detected seismic tremor marked by pulses of seismic energy every 15-20 seconds.

Approximately 24 hours after this activity began, HVO said there were two dozen more earthquakes of magnitude 1.8 to 3.0 that occurred from 1:30 to 6 a.m. on Sunday. Tremors continued as of Sunday afternoon.

They occurred about 27 miles southeast of Naalehu at a depth of 1 to 10 miles below sea level.

“This seismic activity is likely the result of magma movement beneath Kamaʻehuakanaloa seamount and currently shows no sign of leading to an eruption,” said HVO Scientist-in-Charge Ken Hon in a statement. “If the swarm intensifies or changes significantly, HVO will issue an additional notice.”

He continued, “Because of the great depth of the volcano within the ocean and style of Hawaiian eruptions, an eruption of Kamaʻehuakanaloa would pose no threat to the Island of Hawaiʻi. Neither Mauna Loa nor Kilauea volcanoes show any change in activity associated with this earthquake swarm.”

No damage to buildings or infrastructure occurred, and no shaking was felt.

Intermittent earthquake activity has been recorded in the vicinity of Loihi since as early as 1952, according to HVO.

From July to August 1996, there were more than 4,000 earthquakes, with nearly 300 events larger than magnitude 3.0, and 95 events in the 4.0 to 4.9 range.

More recently, a swarm of 100 earthquakes occurred on May 11, 2020, with 18 events in the 3.0 to 3.9 range. A mild earthquake also occurred in June 2021, but did not appear to impact nearby volcanoes.

Since there are no working monitoring instruments on Kama‘ehuakanaloa volcano — whose peak is about 3,280 feet below sea level — all real-time information comes from land-based seismometers on Hawaii island.

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