Earthquake at Lo‘ihi rattles Big Island

A magnitude-4.0 earthquake that struck Wednesday evening below the Lo‘ihi seamount appears to have had no impact on Kilauea or Mauna Loa volcanoes, the USGS said.

The 6:44 p.m. earthquake was centered about 26 miles southeast of Naalehu, under Lo‘ihi seamount, at a depth of 7 miles. Moderate shaking was reported across Hawaii Island, with three reports coming within the first hour of the earthquake.

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According to HVO Scientist-in-Charge Ken Hon, the earthquake had no apparent effect on Kilauea or Mauna Loa volcanoes.

“We see no detectable changes in activity at the summits or along the rift zones of Loʻihi, Kilauea, or Mauna Loa as a result of this earthquake. Aftershocks are possible and could be felt,” Hon said.

Loʻihi seamount is an active volcano on the seafloor south of Kilauea, 19 miles southeast of Hawaii Island’s shoreline. Its summit is 3,280 feet below the surface of the Pacific. The summit area has three pit craters and scientists believe it has a shallow magma chamber about a mile beneath the surface.

Intermittent earthquake activity has been recorded in the vicinity of Lo‘ihi since as early as 1952. The most energetic earthquake sequence occurred in July-August 1996, which included more than 4,000 earthquakes, with nearly 300 events larger than magnitude-3.0 and 95 events in the magnitude-4.0 to magnitude-4.9 range.

More recently, a swarm of 100 earthquakes occurred on May 11, 2020, with 18 events in the magnitude-3.0 to magnitude-3.9 range.

There are no working monitoring instruments on Lo‘ihi. All real-time information about the volcano is derived from land-based seismometers on Hawaii Island.

Loihi is likely to one day break the surface of the ocean and become a new island. Scientists cannot predict how long that would take because it depends on the rate of eruption, but they say it could happen in about 200,000 years.

Seamounts are either active or dormant volcanoes that rise from the bottom of the ocean. They are hotspots for marine life because they carry nutrient-rich water upward from the sea floor.

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Seamounts are believed to cover about 18 million square miles of the planet.

The Associated Press contributed to this report.

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