By Matthew Cappucci
A major magnitude 8.0 earthquake struck roughly 600 miles northeast of New Zealand on Thursday afternoon, triggering concerns of a potentially damaging tsunami.
It’s the third major earthquake in less than eight hours on the Kermadec Fault, which passes east of New Zealand. A magnitude 7.3 hit near New Zealand early on Thursday, followed by a 7.4 about 560 miles to the north a few hours later.
Tsunami waves of 10 feet or greater are possible in the Kermadec Islands, with 3 to 9 foot waves in French Polynesia.
American Samoa, the Cook Islands, Fiji, New Zealand and the Pitcairn Islands can expect water levels fluctuating by up to three feet. A tsunami advisory was issued for American Samoa as well.
A tsunami warning is in effect for New Zealand. The country’s National Emergency Management Agency tweeted “TSUNAMI WARNING issued following Kermadecs earthquake.”
“People near coast from the BAY OF ISLANDS to WHANGAREI, from MATATA to TOLAGA BAY, and GREAT BARRIER ISLAND must MOVE IMMEDIATELY to nearest high ground, out of all tsunami evacuation zones, or as far inland as possible,” they wrote.
Officials in New Zealand urged residents “walk, run or cycle” to higher ground to avoid the chance of becoming stuck in traffic.
A tsunami watch was issued by the Pacific Tsunami Warning Center for Hawaii. First impacts could occur beginning at 4:35 p.m. Hawaii Standard Time, leaving several hours to prepare. Tsunamis travel at roughly the pace of a passenger jet.
“Based on all available data, a tsunami may have been generated by this earthquake that could be destructive on coastal areas even far from the epicenter,” the center wrote.
It was initially unclear what threat exists in Guam, Micronesia and the Northern Mariana Islands.
It is extremely unusual for three severe earthquakes to occur within a 300 mile radius of a point in less than eight hours.
The first two earthquakes occurred far enough apart that they likely were not related. It is probable that the second quake was a foreshock to the third, the stress it released triggering another larger slip nearby. A quake is a foreshock to a larger event less than 5 percent of the time.
The first quake, nearest to New Zealand, released some of its stress horizontally, rather than being a fully “thrust” quake. That minimized the initial tsunami threat. The second quake, much farther north, was a shallow thrust quake, meaning part of one tectonic plate — the Pacific Plate — slid beneath the other, or the Indo-Australian Plate. That’s a recipe for a tsunami, but a serious one did not occur.
The third quake, a severe magnitude 8.1, also appears to have been a thrust quake, and is much stronger. That boosts the odds of a damaging tsunami.
New Zealanders were forced to rush to high ground twice within six hours.
A magnitude 8.0 quake releases about 30 times more energy than a magnitude 7.0 quake. It’s the strongest quake to strike worldwide since May 26, 2019, when a magnitude 8.0 hit Peru.
Already, several aftershocks of magnitude 5 or greater had followed the main earthquake sequence, with a 6.5 quake also observed. Aftershocks should not get too much stronger than that; seismologists use Båth’s Law, which posits that the largest aftershock should be about 1.1 to 1.2 in magnitude less intense than main quake.
This report will continue to be updated as more information becomes available.