Big Island quakes unrelated to volcanic eruption, say scientists - Hawaii News Now - KGMB and KHNL

Big Island quakes unrelated to volcanic eruption, say scientists


There were no reports of damage or injuries after a 4.8 magnitude earthquake shook the Big Island Sunday morning.

The quake took place in the Hilina Region of Kilauea Volcano at 5:54 a.m. The Pacific Tsunami Warning Center said the quake did not generate a tsunami.

The U.S. Geological Survey's Hawaiian Volcano Observatory (HVO) says the magnitude 4.8 earthquake was followed by several aftershocks, the largest of which was a magnitude 3.4 earthquake at 6:06 a.m. The two quakes were recorded on the observatory seismometers

The earthquakes were located five miles south of the summit of Kilauea Volcano, almost directly below the Kulanaokuaiki campground within Hawaii Volcanoes National Park, at a depth of about 20 miles.

According to Wes Thelen, HVO's Seismic Network Manager,  "These earthquakes were most likely structural adjustments of the Earth's crust due to the weight of the island on the underlying mantle. The earthquake likely occurred on a near-horizontal fault plane in the mantle, which has hosted earthquakes in this region before. Despite their location near Kilauea's summit, it's unlikely that the earthquakes were volcanic in nature due to their depth, which is below, and offset from, the volcano's known magma plumbing system."

Thelen said the quake was the earth's crust adjusting to the weight of the island of Hawaii. "Hawaii island imparts a load on the crust and on the underlying mantle. And much like the guy at the bottom of the dog pile, he's kinda squirming to readjust the weight on top of him," he said.

And it's not just the Big Island that does this. All of the islands put a load on the planet. "Even the earthquakes that we've seen north of Molokai and to the northeast of Oahu in the past six months are probably from the same types of forces," said Thelen. "They're just basically responding to the loads of Molokai and Oahu."

HVO Scientist-in-Charge Jim Kauahikaua added that the earthquakes had no apparent effect on Kilauea's ongoing eruptions.  "HVO monitoring networks have not detected any significant changes in activity at the summits or rift zones of Kilauea or other Hawaiian volcanoes."

The earthquake was felt throughout the Island of Hawaii, as well as on parts of Maui and Oahu. According to the USGS "Did you feel it?" website, almost 400 felt reports within the first hour of the earthquake.

"Nothing shook in my apartment, nothing rattled," said Kahului resident Marianne Gill. "But it was enough to jolt me and get me to pay attention."

Kauahikaua said the larger event is only the second earthquake with a magnitude greater than 4 to occur at this location and depth since the start of Kilauea's ongoing East Rift Zone eruption in 1983. The first one occurred on February 17, 2000. There were six such earthquakes in the 20 years before Kilauea's ongoing East Rift Zone eruption began.

Check out our HNN Earthquake Tracker for more information. 

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Related link: USGS Hawaiian Volcano Observatory Webicorders


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