Changes in Tokyo’s population and the soaring number of high-rise buildings over the past 10 years prompted the metropolitan government to begin revising its damage estimate for a major quake directly beneath the capital.

The revised scenario, the first in a decade, is being undertaken to allow for easier evacuation of the 14 million people who make Tokyo their home.

The last estimate released in April 2012 only had one set of conditions for the “Big One,” but the new figures will take into account other aspects, such as quakes of a different magnitude, the season in which they hit or occur in tandem with other natural disasters, typhoons being a particular concern as they have become more frequent due to climate change.

A committee of the metropolitan government’s disaster management council has already held four meetings since November to discuss possible updates. More meetings are scheduled through April and the revised estimate is expected to be released in April or May.

“We want to dig up the weak point of today’s Tokyo and include possible measures,” said one expert who is involved in the discussions.

The last estimate hypothesized a quake of magnitude 7.3 hitting in winter at 6 p.m. when many people would be returning home after work.

But the landscape of Tokyo has changed markedly over the past decade.

The population has increased to about 14 million, much of which is concentrated in high-rise condominiums located along the coastal areas of the capital.

On the other hand, the ratio of homes deemed to be quake-resistant has increased to 92 percent. The ratio of other structures, such as fire and police stations, schools and hospitals, that are now considered quake-resistant stands at a respectable 98.6 percent.

At the same time, there are still parts of Tokyo dotted with many old wooden homes, which pose the risk of fire spreading quickly if a major quake hits. About 10 percent of the total area of the 23 wards in the capital comprise homes of this nature in which 1.826 million people reside, according to one estimate.

Experts are also considering adding a new condition of a quake hitting during the day in summer, which would mean additional problems of trying to evacuate hordes of residents in the searing heat and humidity.

Redevelopment projects over the past 10 years have produced a wealth of new data about the ground foundation in the capital, which will be used for the new estimate, officials said.

Since 2012, the metropolitan government has designated 28 major roads for special construction to allow for easier evacuation and to prevent the spread of fires. Not only have the roads been made wider, but the buildings along the roads have been made more fire- and quake-resistant.

Typhoon No. 19 which hit in 2019 will add another factor to the estimate equation. More than 100 people died or are still listed as missing. Tokyo’s Edogawa Ward for the first time issued an evacuation recommendation and a total of about 35,000 residents sought shelter at 105 facilities.

The latest estimate will also envision a typhoon hitting at the same time as an earthquake. Among the factors to be taken into consideration for the summer scenario is the loss of air conditioning due to power outages as well as communication problems in the event internet and smartphone connections are cut.

With the increase in high-rise condominiums, consideration will also be given to possible damage caused by prolonged earthquake ground motion, which causes tall buildings to sway slowly.

Naoshi Hirata, professor emeritus of seismology at the University of Tokyo, who chairs the metropolitan government committee, said the wealth of new ground foundation data would allow experts to better grasp which areas are more likely to shake during a quake.

He also noted that membership in local disaster management groups is declining due in part to the graying of the population.

“While Tokyo has become safer than 10 years ago, there is still a need to further increase the ratio of homes with quake-resistant measures,” Hirata said. “I urge all residents to stock up on enough food and supplies to survive for at least three days.”