Japan issued its first-ever alert over a possible megaquake along the Nankai Trough on Thursday after a magnitude 7.1 quake struck off the coast of Kyushu earlier the same day, leaving some locals worried about their safety.

“It shook like nothing I’ve ever experienced before,” said a woman in her 50s from the city of Nichinan in Miyazaki Prefecture, the hardest-hit region, on Thursday. “I felt the quake and the fear for a very long time.”

The quake hit the Kyushu region at 4:43 p.m. on Thursday, leaving at least 16 people injured, according to the Fire and Disaster Management Agency. The epicenter was in the Hyuganada sea off the coast of Miyazaki Prefecture.