Submarine images have revealed that the Fukushima quake opened up cracks in the ocean floor as big as 6 feet wide. What effect this may have on future quakes in the area is unknown.
Coincidentally, shortly before the quake, researchers had taken photos of the same area of the seafloor where the crust would later rupture, leading to a tsunami that killed about 20,000 people. This meant that the seabed changes could be documented.
On the MSNBC website, Stephanie Pappas quotes seismologist Takeshi Tsuji as saying that his team of researchers saw open fissures in "many places," but how these cracks may effect future earthquakes along the same fault lines is unknown.