South Korean nuclear safety authorities assured that Tuesday's earthquake off the country's east coast caused no damage to the nation's atomic power plants.

The Nuclear Safety and Security Commission said Wednesday that Wolsong Nuclear Plant located only 51 kilometers from the epicenter of the earthquake reported a peak ground acceleration(PGA) measurement of zero-point-zero-144 g — far less than the maximum PGA of zero-point-two g that the nuclear plant can withstand.

The PGA is expressed as the percentage of the acceleration due to gravity(g), which is approximately 980 centimeters per second squared. 

In South Korea, if the PGA at a nuclear plant is measured at zero-point-one g or higher, operations must be manually stopped. South Korean nuclear plants are designed to automatically shut down operations if the PGA exceeds zero-point-18 g.

A five-point-zero-magnitude earthquake occurred in waters 52 kilometers from Ulsan at 8:33 p.m., marking the fifth strongest tremor to hit South Korea since the country began keeping records of earthquakes in 1978.

A two-point-six-magnitude aftershock followed 41 kilometers off the city some 50 minutes later.