Scientist calls recent earthquakes ‘unusual,’ and here’s why

On Thursday night, many in Hawaii were startled by a 4.2-magnitude earthquake.

The temblor struck at 11:16 p.m. roughly 70 miles north of Hilo, and was felt as far away as Oahu. It did not generate a tsunami.

This was the third notable earthquake recorded this week alone.

On Monday, March 28, at 4 a.m., a 3.6-magnitude earthquake struck near Kihei. Then on Wednesday, March 30, at 3:10 a.m., a 3.8-magnitude earthquake struck off Pahala.

Last week Sunday, March 20, at 6:43 p.m., a 4.5-magnitude earthquake struck near Waikii. View an interactive map of earthquakes here.

Seismic activity in Hawaii is nothing new.

Earthquakes on Hawaii Island occur on a daily basis, though they’re mostly in the 1.0- to 2.0-magnitude range and clustered on the island’s southeast coast. Temblors also rattle near Kona and up through Kohala.

But Paul Okubo, a U.S. Geological Survey research geophysicist at Hawaiian Volcano Observatory, says these particular earthquakes are unusual for three reasons.

“The earthquake magnitudes alone make these unusual. They’re of the size that they are typically pretty widely felt, and that alone makes them kind of interesting,” he said.

Second, the areas where the earthquakes occurred aren’t especially active.

“These are areas that we know we could be exposed to earthquakes, but at the same time, these aren’t the source regions, or the areas where the earthquakes occur that we typically record the largest number of earthquakes from,” Okubo said. “They’re in the active regions but they’re not the most active source regions.”

Third, Okubo noted the timing. All occurred within a few days of each other.

So what does this mean, and could we expect more earthquakes in the future as strong or possibly stronger?

Yes, Okubo says, though there’s no immediate cause for concern.

“The principle that we depend on there is we where we’ve observed large earthquakes, it’s quite likely that we’ll have additional large earthquakes in the future,” he said. “Earthquakes in Hawaii are very closely tied to the active volcanic systems that we have here, and usually, or what we understand is, the more active the volcanoes are, the more seismically active they are as well.”

Generally when we see quakes in Hawaii, they’re due to the massive weight of the mountains pushing on the earth’s crust and more of a structural adjustment versus California, Japan, and Alaska, where there are two large tectonic plates crashing into each other.

Okubo stresses it’s impossible to predict earthquakes, and scientists use past data to create a general idea of when and where earthquakes could occur.

As Hawaii celebrates the 70th anniversary of one of the deadliest tsunamis in Hawaii’s history, Okubo says these earthquakes “are things that help remind us of the need to be aware and somewhat prepared.”

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USGS

M4.2 – 71km NNE of Honoka’a, Hawaii

• Time
• 2016-04-01 09:16:08 (UTC)
• 2016-03-31 23:16:08 (UTC-10:00) in your timezone

Nearby Cities

• 71km (44mi) NNE of Honoka’a, Hawaii
• 105km (65mi) N of Hilo, Hawaii
• 122km (76mi) NNW of Hawaiian Paradise Park, Hawaii
• 131km (81mi) E of Kihei, Hawaii
• 284km (176mi) ESE of Honolulu, Hawaii

http://khon2.com/2016/03/31/scientist-calls-recent-earthquakes-unusual-and-heres-why/