Simpson was in Japan to begin filming her new reality series "The Price of Beauty" when the earthquake hit just southwest of Tokyo, shaking Simpson's home and startling the singer, Us magazine reported.
"Thought I was hallucinating," she wrote on her Twitter site Monday.
"I have never felt anything like this in my life. Laying in bed watching CNN," Simpson wrote.
The singer, who recently split from NFL star Tony Romo, will debut her series on VH1 this year. "The Price of Beauty" will feature Simpson as she tours the globe, finding out how women achieve different standards of beauty on an international scale.
The earthquake struck Japan's Tsuruga Bay at 5:07 a.m. Japanese time and no casualties were immediately reported.