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Hawaii County Civil Defense was activated at 3 a.m. Tuesday in response to a significant increase in seismic activity and deformation — changes in the surface of a volcano — following the collapse of the Puu Oo crater floor on Kilauea’s East Rift Zone. Read more

Hawaii County Civil Defense was activated at 3 a.m. Tuesday in response to a significant increase in seismic activity and deformation — changes in the surface of a volcano — following the collapse of the Puu Oo crater floor on Kilauea’s East Rift Zone.

“We will remain activated through the night until the situation stabilizes,” spokeswoman Kanani Aton said Tuesday afternoon. The county is preparing for “all of it” — potential damaging earthquakes and lava outbreaks, which could affect Highway 130, a major artery.

Meanwhile, scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory were on a 24-hour watch Tuesday to monitor activity.

Residents in lower Puna, including Leilani Estates and Nanawale Estates, felt some of the 200 or so small earthquakes that occurred within a 24-hour period as of 4 p.m. Tuesday, said Janet Babb, USGS HVO spokeswoman.

While some were 3.0-magnitude temblors, the largest was a 4.2-magnitude earthquake at 2:39 a.m. Tuesday offshore south of Puu Oo.

The mayor’s office warned lower Puna residents to remain alert and to check volcano updates. It noted an earthquake at that magnitude does not create risk of a tsunami.

Scientists have been detecting earthquakes and ground deformation in the rift of Puu Oo since April 21, but sudden, dramatic changes occurred several hours after the crater floor collapsed between 2 and 4 p.m. Monday.

“It means the magma was moving somewhere,” Babb said. “Several hours after the collapse it became apparent.”

HVO scientists found an intrusion of magma, which remains below the surface, migrated through the night down toward the lower part of the East Rift Zone, likely beyond Highway 130, Babb said.

A ground crew sent to check the area could not find evidence of ground cracks or steam to suggest magma was nearing the surface Tuesday afternoon, she said.

“An intrusion does not always end up producing an eruption, but it can,” she said. “That’s why we’re watching it very closely.”

As of 6 p.m. Tuesday, seismic activity remained high, but the ground deformation at Puu Oo slowed, Babb said.

Scientists continue to monitor the activity, deploying additional instruments and conducting flyovers.

The county closed the Kalapana lava-viewing area, posted security to keep unauthorized people out and warned not to hike downslope of the rift.

Aton encouraged the public to stay informed by going to hawaiicounty.gov/active-­alert, review their family emergency plan and stock their emergency supply kit.