On Wednesday, a 7.2-magnitude earthquake struck off the coast of Honshu, the country's meteorological agency said.

CNN: Widespread destruction from Japan earthquake, tsunamis

Roughly 30 miles off the coast of Honshu Island in the Pacific Ocean, the Nankai Trough holds an estimated 40 trillion cubic feet of gas hydrates and has received the largest investment and advanced field research of any project in the world.

FORBES

They have since been pushed into the Sea of Japan by a branch of the warm Kuroshio current that is running much closer to land than usual, and have spread up Japan's west coast and even through the Tsugaru strait between Japan's main island, Honshu, and northern Hokkaido into the Pacific Ocean.

ECONOMIST: A netful of trouble for Japanese fishermen