Two magnitude 8.6 earthquakes occurring simultaneously off the Pacific coast would kill up to 27,000 people and leave 30,000 seriously injured, according to a draft report by a government panel obtained by Kyodo News.

A single magnitude 8 quake or a pair of large quakes have occurred in the Nankai trough, which runs through Pacific coastal areas, at intervals of 100 to 150 years. Researchers believe the next quakes could occur as a pair in the first half of this century.

The research panel, made up of experts of the Central Disaster Management Council, also predicts the quakes would cause up to 70 trillion yen in economic damage.

The panel plans to adopt the predictions officially on Thursday. The government is then expected to tell local authorities, including Wakayama and Osaka -- the two prefectures that would be most affected by the quakes -- to reflect them in their disaster measures, they said.

The predictions are based on assumptions of two 8.6 quakes occurring at the same time along the trough, which stretches from waters off Shizuoka to an area off Shikoku, causing shaking with an intensity of 6 or more on the Japanese seismic scale of 7 in many Pacific coastal areas and tidal waves more than 5 meters high.

Of the economic damage, direct damage to homes, office buildings and infrastructure would range from 30 trillion yen to 50 trillion yen, while 4 trillion yen to 8 trillion yen in damage would result from the suspension of production. The severing of major roads and railways would add another 1 trillion yen to 2 trillion yen to the bill.

In December, the panel predicted up to 8,000 deaths from collapsing buildings in major quakes in the region. This time, it added the predicted death toll from subsequent tidal waves and fires.