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.