Town’s 600 earthquakes a week are due to magma reservoir under it, Hawaii study finds

The mysterious source of relentless earthquakes in one Hawaii town has been revealed, and the news will not be comforting to its 1,400 populace.

Turns out Pahala sits atop a massive churning reservoir of magma, according to research published in Science.org.

The town experiences up to 600 earthquakes a week, and the study determined they outline “a region of horizontally layered magma storage deep beneath Pahala,” seismologists at California Institute of Technology reported.

It’s believed the system of “sheeted structures” — known as a sill complex — is nine miles long and up to 26 miles deep.

“Further supporting this idea, long period earthquakes (indicative of the movement of fluids such as magma) are seen occurring within these sills,” the report states.

“Together, these observations demonstrate that deep seismicity beneath Pahala is consistent with the migration and storage of magma within this sill complex.”

Scientists suspect “a zone of volcano-tectonic” earthquakes below Pahala marks a path the magma is moving. Where it’s going hasn’t been confirmed, but it may be flowing to the Kilauea volcano. “However, more evidence is needed to support or refute this hypothesis,” the report states.

The hundreds of weekly quakes at Pahala originate 12 to 25 miles deep, and the largest are felt across the entire Island of Hawaii, officials say.

Pahala was historically the home of a large sugar cane plantation, but it is today known as “a beautiful oasis” where tourists can explore “powerful volcano scenery,” Hawaii-guide.com says.

The town has long been the state’s “most seismically active area,” the USGS says.

However, the tremors have become more frequent in the last five years. All told, the region has experienced nearly 192,000 seismic events in the past 3 and a half years, the report states.

“The jump actually occurred in mid-2019. It’s possible that it is a response to the massive draining from Kilauea (eruption) in 2018,” the USGS says.

“What is known is that the region has been a hotbed of deep seismicity for at least decades — ever since the capability of locating small earthquakes was established in Hawaii.”

This story was originally published January 17, 2023 at 11:30 AM with the headline "Town’s 600 earthquakes a week are due to magma reservoir under it, Hawaii study finds."