A major quake off the coast of central Japan could kill more than 320,000 people and cause 220 trillion yen ($2.3 trillion) in economic damage, a government panel said in a report that more than doubles estimates of the potential cost of such a disaster.

The Cabinet Office said in a report carried by major newspapers Tuesday that the estimates were based on expectations for a magnitude 9 earthquake striking in the Nankai Trough, which runs from just southwest of Tokyo to east of the southern island of Kyushu.

The estimates by the Nankai Trough disaster working group highlight the need for greater preparedness, especially along the heavily populated, industrialized eastern coast, the report said. The government intends to use the higher damage estimate in drawing up disaster preparedness plans.

A magnitude 9 earthquake struck off Japan’s northeastern coast in March 2011, unleashing a massive tsunami that killed nearly 20,000 people and rendered tens of thousands of people homeless, many of them evacuated due to risks from radiation that spewed from the crippled Fukushima Dai-Ichi nuclear power plant.

Two years after those calamities, the government is still just beginning to rebuild, with most of those displaced still living in temporary housing.

But that region was relatively lightly populated and less industrial than the coastal regions of central Japan.

A major earthquake occurs in the Nankai Trough every 100 to 150 years, but one has not happened since an 8.4-magnitude quake in 1854. An earlier, 2003, estimate of damages, based on a scenario of an 8.7-magniitude quake, was 81 trillion yen ($847.3 billion).

The government expects that a worst-case Nankai quake could trigger a tsunami up to 34 meters (111 feet) high, kill some 323,000 people and displace 9.5 million. It would disable water and gas lines, roads and railroads and leave many millions of tons of debris, the report said.

A key concern is the 60 industrial and petrochemical complexes along the coast that could leak chemicals and other toxins into the environment, it said. The report did not outline potential costs from any nuclear accidents that might arise due to such a disaster.

It said Japan’s GDP would drop by over 9 percent in the year following such a disaster. The economy contracted 0.6 percent in 2011 but has failed to regain strong growth despite heavy government spending on rebuilding.

The disaster panel recommended that companies with operations in the regions likely to be worst hit by a Nankai earthquake and tsunami accelerate plans to shift factories further inland or to higher ground.

The panel’s findings may build support for extra government spending on disaster preparedness and retrofitting buildings and other structures to make them more quake resistant. The Cabinet Office’s report said the 169.5 trillion yen ($1.8 trillion) in damage to property and infrastructure could be more than halved if such measures are completed.