Brace yourself, a strong quake is coming.

This dramatic emergency message sent to smartphones and loudspeakers caused a brief panic after midnight Wednesday in Tokyo and neighboring prefectures, with many taking to social media to express their confusion over whether or not to get ready for the worst.

The Meteorological Agency warned of a strong quake off the east coast of Chiba Prefecture at 12:15, warning of possible severe jolts in the capital and Ibaraki, Kanagawa, Saitama and Tochigi prefectures.

The agency warned that a 6.7 magnitude quake could reach lower 5 on the Japanese intensity scale in Ibaraki, but even though a quake did occur, it was relatively weak and unnoticeable in some areas.

“The advance warning system predicting quakes miscalculated the location of the epicenter and predicted a quake of a larger magnitude with more intense shaking,” an official with the agency said in explaining the cause of the erroneous alert.

The agency eventually announced that a quake occurred east of Chiba at a depth of about 30 km and with a magnitude of 4.6. In some areas in southern Ibaraki and northeastern Chiba Prefecture, the jolts were recorded at level 4 or lower on the intensity scale.

The tremor didn’t trigger tsunami, the agency said.

According to the agency’s website, it sends out emergency warnings to areas expected to experience an intensity of 4 or stronger when a quake of lower 5 or greater is estimated to occur.

The alert may have triggered deja vu in many residents.

In January, the agency issued a false alert to residents of the Kanto region and parts of Fukushima Prefecture, warning of a strong quake that never came. In August 2016 the agency issued an erroneous alert for a level 7 quake, highest on the seismic intensity scale.

“Well, such (errors) are quite rare but they do happen,” the agency official admitted.

After the alert, Twitter blew up with reactions.

“You woke us all for this? It’s not even shaking,” wrote Twitter user @B_SatyaKishore.

Another user with the handle @Ayumi511010 suggested the outcome should be seen positively.

“We shouldn’t complain that despite last night’s quake alert ‘nothing serious happened,’ but should be happy the quake wasn’t serious. False alarms are welcome. We can see it as a drill that will prepare us for a day when a big one strikes,” the user wrote.

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