Magnitude-4.3 quake deep under Pāhala jolts Big Island late Sunday night

Imagine watching as lava fountains erupt from the summit crater of Kīlauea — one of the most active volcanoes on the planet — while lava flows around the caldera, when out of nowhere a large earthquake rocks the ground underneath your feet.

Especially when seismic activity on the volcano itself, despite the ongoing eruption, has been surprisingly low.

“All those days of no quake activity was for a reason,” commented one of the people on the live chat of the livestream watching the ongoing Kīlauea summit eruption Sunday night after a magnitude-4.3 earthquake struck the Big Island near Pāhala, about 23 miles southwest of Hawai‘i Volcanoes National Park where the volcano’s summit is located.

Hawaiian Volcano Observatory reported the quake happened at 11:04 p.m. and was centered about 1 mile west-southwest of the Kaʻū community at a depth of 19 miles below sea level.

It was followed by several aftershocks late Sunday and early Monday:

• A magnitude-3.7 quake at 11:19 p.m. about 1.2 miles southwest of Pāhala at depth of nearly 19 miles.
• A magnitude-2.6 quake at 11:27 p.m. about 1.2 miles southwest of Pāhala at depth of nearly 19 miles.
• A magnitude-2.7 quake at 11:35 p.m. almost 2 miles west-southwest of Pāhala at depth of nearly 20 miles.
• A magnitude-2.6 quake at 1:06 a.m. about 1 mile southwest of Pāhala at depth of nearly 19 miles.

Additional aftershocks are possible in the coming days to weeks.

No damage to buildings or infrastructure was expected based on the earthquake’s intensity, which was recorded as only light shaking according to instrument readings and members of the public who reported they felt the temblor.

“That was a jiggler,” posted Darlene Springer in the Ocean View Hawai‘i Community Bulletin Board group on Facebook just 3 minutes after the quake rocked the island.

“Yes it was. Woke me up,” replied Tim Reed.

“WOWWWW,” exclaimed Paul Lowe.

One person in the live chat of the Kīlauea eruption livestream said it wasn’t at all a shaking they felt on Nāpō’opo’o Road in Captain Cook; “It was more like a very strong jolt.”

There were more than 265 “Felt” reports made to the U.S. Geological Survey within the first 40 minutes after the quake. The top 5 areas with the most were:

• Nāʻālehu with 44.
• Kailua-Kona with 39.
• Captain Cook with 35.
• Mountain View with 20.
• Hilo and Waimea tied with 16 each.

“Did Kilauea just go Boom again?” posted Thomas Tucker Jr. at 11:09 p.m. in the Ocean View Hawai‘i Community Bulletin Board group. “Just felt quite the shaker.”

There also was one “Felt” report each from as far away as Honolulu and Kailua, O‘ahu, both more than 200 miles from Pāhala.

Seismic activity has been relatively low for about the past month, with just 10 earthquakes reported felt throughout the Hawaiian Islands since Nov. 28, based on a quick count of those listed in “Volcano Watch” articles from Hawaiian Volcano Observatory since the beginning of December.

That includes a magnitude-4 quake Nov. 30 centered 10 miles west-northwest of Volcano, the largest of the 10 reported felt.

There also was a magnitude-2.6 earthquake at 1:42 p.m. Sunday, about 7 miles southwest of Laupāhoehoe at a depth of 16 miles below sea level. It had just on “Felt” report that came from Kailua-Kona, almost 71 miles away on the opposite side of the island.

Quake activity at the Kīlauea summit has also been low, despite an eruption happening.

Hawaiian Volcano Observatory reported Sunday in its daily update that there were no detected earthquakes in the summit region between Saturday and Sundy morning.

Even seismic tremor associated with the eruption remains low.

Tremor has hiked gradually since Dec. 28, however, with a renewed increase in fountaining vigor during this more recent episode of the eruption, which is confined within Halema’uma’u Crater and the downdropped block inside Kaluapele, the summit caldera, in Hawai’i Volcanoes National Park.

Shallow earthquake counts on the East Rift Zone and Southwest Rift Zone of the volcano also remain at low levels.

There was one quake in the middle East Rift Zone and one in the Southwest Rift Zone between Dec. 28 and Sunday.

“Something is happening with [the] supply chamber deep under the island,” conjectured the citizen scientist chatting on the eruption livestream at the time of the earthquake Sunday night.

The chatter added that the earthquake could signify a stronger pulse of magma moving deep below Pāhala or even a fault slip, as deep under the community is where magma rises up through the Earth’s crust.

“The Pāhala region sits at the structural nexus between three volcanoes — Kīlauea, Mauna Loa and [Kamaʻehuakanaloa],” said a May 20, 2021, “Volcano Watch” article about new research into the increase of earthquake activity since 2019 beneath Pāhala.

Some suggest the deep region beneath the community is a pathway for magma from the upper mantle plume beneath the Big Island to Kīlauea, causing earthquake numbers to spike when magma is supplied to the volcano.

However, there is no direct evidence to support that.

There is now a hypothesis that some magma could be leaking from the mantle plume and migrating into the Pāhala region, stalling at depth.

So while there is no direct evidence magma is accumulating deep under Kaʻū, the volcano observatory wrote that it is interesting to think the liquid rock could be pressurizing the region, increasing the number and variety of earthquakes.

It is a hypothesis that definitely warrants more investigation.

“The Pāhala earthquake swarm in its current state appears to be a unique occurrence that has not previously been observed in Hawai‘i,” the “Volcano Watch” article said.

Hawaiian Volcano Observatory reported Sunday’s earthquake was part of the ongoing swarm of deep seismicity that has been happening beneath the Pāhala area since 2019.

It also had no apparent impact on either Kīlauea of Mauna Loa volcanoes.

No matter what caused the quake, however, the citizen scientist in the live chat hoped it would mean more lava erupting in the summit crater, with enough to make the fountains 300 feet high again.

Hawaiian Volcano Observatory continues to monitor Hawaiian volcanoes for any changes.

It also continues keeping a close eye on Kīlauea as the summit eruption persists and remains in close contact with Hawai‘i Volcanoes National Park and Hawai‘i County Civil Defense.