5.5-magnitude Big Island temblor was an aftershock from large 2018 quake

5.5-magnitude Big Island temblor was an aftershock from large 2018 quake
This map shows earthquakes on or near Hawaii Island since May 2018. (Image: USGS)

HONOLULU (HawaiiNewsNow) - The 5.5-magnitude quake that jolted Big Island residents from their beds early Wednesday was actually an aftershock from a large temblor that rocked the island last year, scientists say.

In fact, it was the biggest so far of the thousands of aftershocks from the quake.

Hawaiian Volcano Observatory geologists say the earthquake Wednesday ― which happened about 1 a.m. ― didn’t originate from Kilauea volcano’s summit region.

Instead, it was centered about seven miles south-southeast of Volcano village and at a depth of about four miles below sea level. Earthquakes that happen there are due to movement along a fault line ― not volcanic activity.

Last May’s magnitude-6.9 quake was blamed on that fault ― as was a magnitude-7.7 that happened in 1975.

And aftershocks from the 1975 earthquake, the largest in Hawaii in the last century, went on for decades.

Geologists say that Hawaii Island could similarly see aftershocks from the 2018 quake for years to come.

“It is generally understood that aftershock sequences could include earthquakes as large as one magnitude unit lower than the mainshock magnitude,” the Hawaiian Volcano Observatory said, in an online post. “In this regard, while not strictly predictable, this magnitude-5.5 was expected. And, we expect aftershocks to persist for several more years.”

The key takeaway, though: The earthquake doesn’t mean any increase in volcanic activity at Kilauea. On the contrary, the scientist say, it’s “part of an evolution of Kilauea seismicity back to more typical levels.”

Copyright 2019 Hawaii News Now. All rights reserved.