Note: Map shows the area with a shake intensity of 3 or greater, which U.S.G.S. defines as “weak,” though the earthquake may be felt outside the areas shown. The New York Times
A major, 7.8-magnitude earthquake struck in the Celebes Sea near the Philippines on Monday, raising the possibility of a tsunami for the country’s coastlines, according to United States monitoring agencies.
A tsunami advisory has also been issued for Guam, according to the U.S. Tsunami Warning System. There was no threat to the Pacific coastlines of the United States and Canada, the agency said.
The temblor happened at 7:37 a.m. Philippine time about 15 miles southwest of Burias, Philippines, data from the U.S. Geological Survey shows.
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.
Experts warn that just before a tsunami hits shore, seawater can first be drawn out to sea — exposing large swaths of beach and giving people along the water a false sense that a coast is safe.
Aftershocks detected
Subsequent quakes have been reported in the same area. Such temblors are typically aftershocks caused by 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
The New York Times
As more information becomes available, officials may update, add or cancel tsunami alerts and 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.
Sources: United States Geological Survey (epicenter, aftershocks, shake intensity); LandScan via Oak Ridge National Laboratory (population density) | 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 Philippine time. Shake data is as of Sunday, June 7 at 7:56 p.m. Eastern. Aftershocks data is as of Sunday, June 7 at 9:24 p.m. Eastern.