A swarm of over 130 small, shallow earthquakes that occurred Thursday and Friday on Kilauea signals neither an imminent threat of an eruption nor a large quake, the U.S. Geological Survey Hawaiian Volcano Observatory announced Friday afternoon.
“We’re not expecting any intrusion or any eruption based on all the data streams we see, but in terms of earthquakes, we really can’t say,” said David Phillips, USGS HVO acting scientist-in-charge. “We can’t really rule it out.”
At times there have been earthquakes after swarms, but not at other times, he said.
Hawaiian Volcano Observatory detected the temblors along the Kaoiki fault system northwest of Kilauea’s summit and west of Namakanipaio Campground inside Hawai‘i Volcanoes National Park.
The campground has been closed, as much of the park has been, due to the pandemic.
“Because this fault system is along the boundary between the volcanoes (Kilauea and Mauna Loa), there’s no source of magma,” Phillips said.
Other data that is monitored, including ground deformation — meaning changes in the shape of the earth’s surface, gas emissions and visual geologic changes — shows no indication of increased activity connected with this swarm.
This is in contrast to the 2018 eruption on Kilauea’s lower East Rift Zone, when HVO tiltmeters measured dramatic changes in the shape of the ground due to pressure within the volcanic system and the accumulation and migration of magma, Phillips noted.
Most of the quakes over the past two days were less than magnitude 2, and the largest was a magnitude-3 earthquake.
They were occurring in a cluster about a mile wide and 1 to 3 miles beneath the surface, the USGS reported.
Most Hawaii island residents either didn’t feel it or reported feeling weak shaking. But others did, like Phillips, who lives in the Volcano Golf Course subdivision, the closest residential area to the epicenter.
“I did not get much sleep last night,” he said. “Just when I was falling back to sleep, bang! — there’s another one.”
But surprisingly few residents in nearby Volcano Village felt it, he said. “It was very localized.”
By Friday afternoon the activity had slowed, Phillips said.
He said a lot of these quakes are associated with gravity, adding that the whole stress system is settling since the 2018 eruption, which could trigger changes in the pressure within the volcano.
The volcanoes are “recharging, with new magma entering the primary system,” Phillips said.
“Even though Kilauea and Mauna Loa are not currently erupting, there is constant ‘background’ activity going on within these volcanoes, which can lead to things like this swarm,” he said.
The Kaoiki Pali area had a similar swarm Feb. 22-24, 2012, when 180 earthquakes, the largest a magnitude-4.3, shook the area.
Swarms in the area go back to November 1983, when a magnitude-6.6 earthquake caused $6 million in damage.
That quake changed how susceptible the area is to seismicity.
Prior to that, only five major quakes and no seismic swarms occurred. After that the average number of seismic swarms at least tripled.
HVO continues to closely monitor geologic changes 24/7, and will issue messages and alert level changes as warranted, it said.
