NEW : Six people were killed and three injured in Tuesday 's quake . It was centered about 77 miles east-southeast of Tokyo . Threat level now on par with Chernobyl . The epicenter is a shallow, narrow trench that runs along the Pacific Ocean floor for hundreds of kilometers ( miles). The earlier quake prompted workers at the Fukushima Daiichi plant to evacuate briefly .
NEW : Six people were killed and three injured in Tuesday 's quake . It was centered about 77 miles east-southeast of Tokyo . The epicenter is a shallow, narrow trench that runs along the Pacific Ocean floor for hundreds of kilometers ( miles). The earlier quake prompted workers at the Fukushima Daiichi plant to evacuate briefly .