Photo/Illutration Kyoto University professor Satoshi Fujii, left, a member of the Japan Society of Civil Engineers, speaks at a news conference in Tokyo on June 11. (Fumi Yada)

A long-feared megaquake along the Nankai Trough could cause 1,466 trillion yen ($10 trillion) in damage, experts said, revising up their previous estimate by 56 trillion yen.

The earthquake would lead to 225 trillion yen in direct damage and 1,241 trillion yen in economic damage in a worst-case scenario, the Japan Society of Civil Engineers said June 11.

Devastation of roads, ports and factories would hurt regional economies so bad that they would need more than 20 years to recover, the society said.

The government’s Earthquake Research Committee said in January there is an approximately 80-percent probability of a magnitude-8 to -9 earthquake occurring along the Nankai Trough within the coming 30 years.

The elongated depression in the Pacific Ocean floor stretches from the Tokai to Kyushu regions. The area has a history of being struck by megaquakes roughly once every 100 to 150 years.

The most recent ones, both with a magnitude of around 8, hit off the Kii Peninsula in 1944 and 1946.

The first one killed about 1,200 people, many in the Tokai region, while the second left about 1,400 dead or missing, mainly on the island of Shikoku.

The damage estimate increased from the figure included in the society’s interim report published in 2018 as rising prices of goods and services have more than offset improvements made to social infrastructure in recent years.

However, if more than 58 trillion yen is spent beforehand on measures to mitigate the impact of the temblor, economic damage would decrease by 396 trillion yen, or about 32 percent, the group said.

In March, the Cabinet Office released a report that estimated about 225 trillion yen in direct damage to buildings and infrastructure from a magnitude-9 level Nankai Trough earthquake. Indirect damage from decreased productivity and other reasons was estimated at about 67 trillion yen.

“The government failed to evaluate shrinking of industries and other effects,” Kyoto University professor Satoshi Fujii, a member of the Japan Society of Civil Engineers, said. “We also need to properly factor in a decrease in quake victims’ incomes.”

The group also said a magnitude-7 level earthquake directly striking Tokyo would cause 1,110 trillion yen in direct and economic damage combined.

The amount increased by 109 trillion yen from a previous estimate released last year after higher prices and other changes were taken into account.

Proactive measures worth more than 21 trillion yen would squeeze economic damage by 410 trillion yen, the group said.

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