The Pacific Northwest was hit hard by the quake that killed at least six people and left at least 13,000 people without power in Washington state and Idaho.
The U.S. Geological Survey said Thursday the magnitude 7.8 quake was centered about 75 miles (120 kilometers) west of the town of Mukilteo, Wash.
The epicenter was located about 20 miles (32 kilometers) north of Seattle.
In Spokane, the quake struck just after 9 a.m.
The U.K.’s Meteorological Office said it was also under a state of emergency as a result of the quake.
The Washington state Department of Emergency Management and Emergency Management (DEEM) issued a tsunami warning for areas of the Cascade Range near the epicenter, and it said the tsunami warning was in effect for all but the largest towns of Kent and Spokane, where the quake occurred.
The warning extends to the coastal waters of the Puget Sound, the eastern slopes of the Columbia River, the northern portions of the Sierra Nevada and western portions of Alaska.
The agency said in a news release that it has issued tsunami warnings for most areas of Washington.
The state is under a tsunami alert and will be releasing tsunami advisories for those areas beginning at 4 p.m., according to DEEM.
The earthquake struck near the top of a major fault line in the ocean crust, and as it struck, it was the largest magnitude earthquake in U.s. history, the U.N. said.
The quake’s epicenter is roughly 100 miles (161 kilometers) east-northeast of Muklteo.
The USGS has measured the quake’s magnitude at 6.9.
It was a magnitude 7 on the Richter scale, which is considered to be the strongest.
In its update on the magnitude, the USGS said the quake was the strongest since March 2016, when a magnitude-6.6 earthquake struck in the city of Mukluk, Alaska.
The magnitude 7 quake also was the second-strongest in the Us. since at least 1900.
The epicenter of the Mukluke quake was located just northwest of the coast in the Aleutian Islands, and the epicenters of the other two major earthquakes occurred in Alaska.
Both earthquakes were caused by faults that were part of the Pacific Plate.
In the case of the Aleuts, the Pacific plate was moving east and was traveling away from the North American Plate.
The Pacific plate is now sliding westward, and scientists have found that the Pacific Ring of Fire, a ring of faulting that extends from the Pacific to the Atlantic oceans, is slowly shifting toward the Pacific Ocean.
Scientists are still trying to determine the cause of the earthquake, and experts believe it could be related to the Pacific’s rotation.
The Pacific Plate is also moving away from Asia and toward Europe.