Just more than 24 hours after powerful earthquakes struck a large island in southwest Japan, an even stronger quake has hit the same area.

The Associated Press quotes a Japanese official as saying 19 people were killed, bringing the total for the two big quakes to 29.

On Thursday evening local time, magnitude 6.2 and 6.0 quakes shook the city of Kumamoto and the surrounding area. They were followed by more than 100 smaller temblors, according to NHK — including several registering 5.0 or stronger, the U.S. Geological Survey says. The series of quakes shattered buildings. Hundreds of others were injured.

Then at 1:24 a.m. on Saturday, a magnitude 7.0 quake hit nearly the same location,according to the USGS. It was quickly followed by aftershocks of magnitude 5.8 and 5.7. (Japan is 13 hours ahead of the U.S. East Coast.)

The latest earthquake isn't considered an aftershock; instead, the quakes yesterday were foreshocks of the 7.0 quake, NPR's Nell Greenfieldboyce explains. She tells our Newscast unit that according to the USGS, the new quake "is six times larger than the biggest one yesterday and released 16 times more energy."

The USGS also says the 7.0 earthquake, like those on Thursday, was shallow — which is unusual for the region and can increase the degree of shaking and damage.

"I wouldn't be surprised to see more damage — I wouldn't be surprised to see more casualties than yesterday," John Bellini, a geophysicist with the USGS, tells our Newscast unit. - Read More 

After Powerful Quakes, An Even Stronger Temblor Strikes Southern Japan