Japan was struck by a major aftershock Thursday night triggering a tsunami warning for the same area hit last month by a devastating earthquake and tsunami.

The tsunami didn’t materialize, and the warning was lifted. Measured at 7.4, the quake shook buildings in Tokyo and left seven people injured. No damage was reported at the crippled Fukushima Daiichi nuclear power facility; however workers were evacuated from the plant. Electricity went out in much of northern Japan, a region where the power grid is only beginning to be restored following the March 11 temblor.

Work continued at the Fukushima site where nitrogen is being pumped into a damaged reactor in an effort to prevent an explosion of hydrogen gas. Radiation levels at two other nuclear plants remained normal. The Onagawa and Higashidori plants have also been out of commission since last month’s quake. The 9.0 magnitude March quake left 28,000 people dead or missing.