Rare Earthquake Swarm Rocks Lō’ihi Seamount South of Kilauea Volcano Off Hawaii’s Big Island

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Beginning about 3:00 a.m. HST on May 11, 2020 and continuing through the morning of May 12, HVO detected more than 100 earthquakes beneath Lōʻihi, including 79 magnitude-2 (M2) and 19 magnitude-3 (M3) and above.

Does it indicate that a submarine eruption has occurred or is brewing and are there significant hazards of concern to the Island of Hawaiʻi at this time?

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Lō’ihi Seamount earthquake swarm in May 2020 in Hawaii. Map via USGS

Volcanologists are keeping a close eye on their instruments after a rare earthquake swarm hit off the Big Island the past two days.

Twenty miles off the southeast coast of the Big Island, Hawaii’s newest volcano rises 10,000 feet from the ocean floor with its summit about 3,000 feet under the surface.

When Loihi starts shaking, scientists pay attention. “Think of it as a younger version of Kilauea or Mauna Loa volcanoes,” said David Phillips, deputy scientist in charge at Hawaiian Volcano Observatory.

No significant hazard… But

Phillips said there’s no significant hazard at the moment, but at one point HVO recorded 14 earthquakes per hour on the Loihi Seamount.

The peak did take place yesterday afternoon, whether it continues to subside or come back is hard to say,” Phillips said.

On a seismogram, more than a hundred temblors struck in the 2- to 3-magnitude range, suggesting magma is on the move.

Phillips said if the shaking continues, it could signal an eruption — and that could cause a summit collapse.

That’s happened before, last in 1996. A significant eruption could even cause a small tsunami.

There would be very little time to respond,” Phillips said. “It would be certainly less than an hour, could be minutes.

But there is no sign of trouble right now. “From everything we’ve seen, there’s nothing like that coming,” Phillips said.

The seismic unrest

The earthquake swarm is located beneath the southeast rift zone and southeastern flank of Lōʻihi at depths of 3.6 to 12.4 km (2.2 to 7.7 mi) below sea level or approximately 1 to 9.8 km (0.6 to 6 mi) below the volcano’s surface.

Beginning about 3:00 a.m. HST on May 11, 2020 and continuing through the morning of May 12, HVO detected more than 100 earthquakes beneath Lōʻihi, including 79 magnitude-2 (M2) and 19 magnitude-3 (M3) and above.

This is a significant increase above long term background rates of fewer than 3 earthquakes per day at Lōʻihi, generally with magnitudes less than 2.

The number of earthquakes peaked at 14 per hour between 1 and 2 pm on Monday afternoon and decreased thereafter. Since the early morning hours of May 12, earthquake rates have been less than 4 per hour.

Geologic background

LOIHI seamount is an active volcano on the seafloor south of Kīlauea Volcano, about 30 km (19 miles) from the shoreline of the Island of Hawaiʻi.

The top of the seamount is about 975 m (3,199 feet ) below sea level. The volcano consists of a broad summit area marked by three pit craters and two prominent rift zones extending from the summit about 22 km (13.6 mi) south-southeast and about 15 km (9.3 mi) north-northeast.

The volcano likely has a shallow magma chamber between 1 to 2.5 km (0.6 to 1.6 mi) deep below the summit.

Earthquake activity has been recorded near Lōʻihi since 1952. Prior Lōʻihi earthquake swarms occurred in 1952, 1971–72, 1975, 1986, 1988, 1990, 1991, 1996, 2005, and 2017, and were characterized by hundreds to thousands of earthquakes occurring over weeks to months with magnitudes ranging up to M4.9. The largest earthquake detected at Lōʻihi was a M5.1 in May of 2005.

Many of the 1952 Lōʻihi earthquakes were felt in coastal communities and one of the earthquakes generated a small tsunami that swept inland about 180 m (600 ft) at Kalapana; no damage was reported. The 1996 Lōʻihi earthquake swarm was one of the most intense earthquake swarms recorded by the HVO monitoring networks.

Meanwhile, the seamount appears to have settled down. Besides the occasional rumble, the most exciting things on Loihi are the creatures that thrive in the hot water nearly a mile deep.

Get ready for the next eruption on Strange Sounds and Steve Quayle. [USGS, Hawaii News Now]

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2 COMMENTS

  1. Lo’ihi is not the problem
    but the Hilena slump is.
    The Hilena slump is part of the large volcano Mauna Loa and located below sea level on the south side of the volcano.
    Now, just mile as away from the Hilena slump is Loihi.
    Another worry is the continuous rumblings taking place around the Hilena slump.
    Both the small magnitude earthquakes on the south side of Mauna Loa and the more than active Loihi is of grave but unreported concern by the scientist.
    Below is a video of what will happen if the Hilena slump slides into the ocean.
    https://www.youtube.com/watch?v=VvMUJKFjAiA

  2. ALL you guys would be so much better informed if YOU LISTENED TO THE LORD,He says..MAUNA LOA IS GOING TO BLOW UP AND THE ISLAND will disappear below the sea,and KILL everyone on the island,and I’am USGS knows it,but they never tell the truth about about anything,their just like NASA,never the truth..AND WORSE ..YELLOWSTONE will kill millions very soon,they won’t warn about that either….

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