A small fishing boat, rear, is washed aground on a breakwater as a roof sits on what was once a wharf of a port on Okushiri Island, off the southwestern coast of Hokkaido, in this file photo taken on July 14, 1993, one day after a major earthquake shook the island and a tsunami flattened the seaside area.

(AP Photo/File, Katsumi Kasahara)

At a Glance

On July 12, 1993, a magnitude 7.8 earthquake struck in the Sea of Japan.A resulting tsunami hit Okushiri island, where at least five boats simultaneously combusted.

Fires that consumed a Japanese port in the wake of a 1993 earthquake-triggered tsunami were likely caused by methane gas released from the seabed during the tremor, a Japanese scientist said.

On July 12, 1993, a struck in the Sea of Japan, triggering a tsunami that crashed into Hokkaido and Okushiri islands in northern Japan, according to the U.S. Geographical Survey. As the monster wave hit the smaller outlying Okushiri, at least five boats moored in the island's Aonae Harbor simultaneously burst into flames. The tsunami waves and high winds drove the flames inland, where numerous buildings in the port were consumed by the fires.

Yuji Enomoto, a professor emeritus at Shinshu University in Japan, studied footage of the event taken by Japan's news agency NHK. He conducted lab experiments based on the footage and determined the fires resulted from methane gas released from , Live Science reported.

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Enomoto and his team believe the methane combusted when high winds slammed the gas into Aonae Harbor's quay wall, along with methane bubbles on the boats that burst into flames. Oil and gas leaking from a vehicle at the harbor further fueled the flames.

Last week at the annual meeting of the American Geophysical Union, Enomoto explained to Live Science that eyewitness accounts reported "mists rising and seawater 'foaming'" as the tsunami approached. He suggested the foaming could have been the result of methane gas carried by the tsunami waves.

Enomoto noted that with the amount of methane gas buried beneath the seafloor off the coast of Japan, further analysis is needed to heed off potentially disastrous consequences from methane gas-triggered fires should disaster strike again.

An estimated , 190 people were injured and 160 were reported missing in the aftermath of the 1993 quake and tsunami, the New York Times reported.