This is a developing story. This post will be updated.

A massive earthquake erupted along a fault line near the Solomon Islands in the southwest Pacific Ocean on Thursday. The quake was originally detected as a magnitude-8 by the U.S. Geological Service, but has since been reduced to a 7.8 on the Moment-Magnitude scale.

It was followed by a 5.5-magnitude quake, and aftershocks continue to roll through.

Immediately after the quake, a tsunami watch was issued for Hawaii by the Pacific Tsunami Warning Center. Water height fluctuations were recorded by at least three surrounding buoys, but after investigating, the center determined there was no threat to the island state.

“I always want to tell people that there’s possibility, with a quake this size, there’s certainly a possibility,” Don Blakeman, a geophysicist for the USGS, told Hawaii News Now.

As a precaution, the Pacific Tsunami Warning Center, part of NOAA, issues a watch immediately after any earthquake that has the potential to generate a tsunami. It then analyzes the data to determine the threat, at which point it is changed to a warning or advisory, or canceled altogether.

Moderate to heavy shaking was reported on the island of Makira, which was the closest to the epicenter of the quake. Strong shaking was reported near the capital of Honiara, north of the epicenter.

Over 500,000 people live on the archipelago located east of Papua New Guinea. In 2007, a magnitude-8 earthquake struck the islands and generated a tsunami that may have been over 30 feet high, according to the Solomon Islands Foreign Office, though it’s difficult to pinpoint the exact height.

In nearby Australia, the Bureau of Meteorology has given the all-clear after Thursday’s quake. No tsunami is expected there.

Thursday’s earthquake is tied for the strongest on Earth in 2016 with the Ecuador, New Zealand and Indonesia quakes. More than 650 people died when the 7.8 earthquake rocked Ecuador on April 16.

Earlier on Thursday, a 6.5-magnitude quake rumbled off the coast of Northern California just before 7 a.m. Pacific time. The epicenter was just 6.2 miles deep, which is a very shallow earthquake, though no tsunami warnings were issued. Even though the quake was considered strong, it did not translate into strong shaking in California.