Magnitude 7.0 and 5.8 earthquakes off the coast of Northern California have prompted a rare tsunami warning for coastal areas near the California-Oregon state line, including San Francisco Bay.
Confusion ensued after a Tsunami Warning was issued Thursday minutes after an earthquake was detected off the Northern California coast and canceled soon after.
The Tsunami Warning, which means a tsunami with flooding and dangerous currents is imminent, was issued for the area from just south of Florence, Oregon, down to Davenport, California, when the 7.0 magnitude quake struck less than 40 miles off the coast of Northern California.
One of the metropolitan areas included in the alert was San Francisco, where evacuation orders were issued and residents were advised to flee to higher ground.
A view of Pacific Coastline in Pacifica, California, United States on December 5, 2024 as tsunami warning issued after 7.0 magnitude earthquake reported off Northern California coast.
(Photo by Tayfun Coskun/Anadolu via Getty Images / Getty Images)
After 70 minutes and no signs of a tsunami, the Tsunami Warning was canceled, leaving many in the warning zone frustrated.
To explain the reasoning behind the Tsunami Warning, the National Weather Service posted a thread on X, formerly Twitter, to help the public understand their process for the warning.
WHAT IS A TSUNAMI AND WHAT CAUSES THEM?
They provided a timeline of events, from when a preliminary assessment detected an earthquake at 10:44 a.m. PT to when the NWS National Tsunami Warning Center issued the Tsunami Warning five minutes later at 10:49 a.m.
A 7.0 magnitude earthquake in northern California on Dec. 5, 2024.
(FOX Weather)
The NWS noted that the quick issuance of the Tsunami Warning was due to the fact that tsunami waves can travel as quickly as 500 mph in the deep ocean. Additionally, the NWS said, an earthquake with a magnitude of 7.0 is capable of producing a damaging local tsunami.
These critical factors prompted the NTWC to issue the Tsunami Warning to provide people ample time to evacuate, should a tsunami make its way to shore. In the meantime, the NTWC can continue to analyze data about the earthquake and any tsunami waves it may have produced.
When no damaging tsunami threat became evident, the NTWC canceled the Tsunami Warning at 11:54 a.m.
Pedestrians on Ocean Beach after a tsunami warning in San Francisco, California, US, on Thursday, Dec. 5, 2024.
(David Paul Morris/Bloomberg / Getty Images)
The NWS acknowledged how the issuance and quick cancellation of the warning may have frustrated or angered some people, particularly those who evacuated. However, they stressed the importance of the warning given the deadly nature of tsunamis caused by earthquakes.
“If you evacuated, you did the right thing,” they said. “Tsunamis are rare, but can be extremely deadly. For perspective, roughly 230,000 people lost their lives in the 2004 Indian Ocean Tsunami, the deadliest natural disaster of the 21st century.”
“We understand the confusion and disruption this warning caused,” they added. “Hopefully this thread helped clear up the warning process and rationale. The National Weather Service strives to reduce false alarms while protecting life and property.”
The official tsunami measurements by the National Tsunami Warning Center after the earthquake on Dec. 5, 2024.
(National Tsunami Warning Center / FOX Weather)
The NTWC noted that they did measure a 9-cm (3.54-inch) peak at Arena Cove, California, which lies north of San Francisco, at 11:46 a.m. PT. Still, they cautioned residents of the potential dangers after an earthquake.
“Remember, the first wave may not be the largest or last,” the NTWC posted on Facebook. “And unusual and strong currents may be found locally for hours or days following this event.”