Note: Map shows the area with a shake intensity of 4 or greater, which U.S.G.S. defines as “light,” though the earthquake may be felt outside the areas shown. The New York Times
A major, 7.8-magnitude earthquake struck in the North Pacific Ocean on Thursday, according to the United States Geological Survey. The earthquake prompted a tsunami advisory, the second-highest alert level, for some coastal portions of western Alaska.
The temblor happened at 2:58 p.m. Eastern about 80 miles east of Petropavlovsk-Kamchatsky, Russia, data from the agency shows.
The tsunami advisory was in place for parts of the Alaskan coast that were closest to the earthquake.
Tsunamis are a series of long waves caused by a large and sudden displacement of water in the ocean, usually from a large earthquake on or below the ocean floor. Tsunamis radiate in all directions from the epicenter and can cause dangerous coastal flooding and powerful currents that can last for hours or days.
The Pacific Tsunami Warning Center in Honolulu said it was too soon to tell whether tsunami waves might threaten Hawaii, noting that the earliest any threat might reach the islands would be 2:51 p.m. local time.
In late July, the same region was hit by an 8.8-magnitude earthquake. That quake, one of the strongest ever recorded, set off tsunami waves that reached as far away as Hawaii and California.
As seismologists review available data, they may revise the earthquake’s reported magnitude. Additional information collected about the earthquake may also prompt U.S.G.S. scientists to update the shake-severity map.
Aftershocks in the region
An aftershock is usually a smaller earthquake that follows a larger one in the same general area. Aftershocks are typically minor adjustments along the portion of a fault that slipped at the time of the initial earthquake.
Quakes and aftershocks within 100 miles
Aftershocks can occur days, weeks or even years after the first earthquake. These events can be of equal or larger magnitude to the initial earthquake, and they can continue to affect already damaged locations.
When quakes and aftershocks occurred
Source: United States Geological Survey | Notes: Shaking categories are based on the Modified Mercalli Intensity scale. When aftershock data is available, the corresponding maps and charts include earthquakes within 100 miles and seven days of the initial quake. All times above are Eastern. Shake data is as of Thursday, Sept. 18 at 3:16 p.m. Eastern. Aftershocks data is as of Thursday, Sept. 18 at 4:14 p.m. Eastern.
Maps: Daylight (urban areas); MapLibre (map rendering); Natural Earth (roads, labels, terrain); Protomaps (map tiles)
