The government called for an electronic mapping system Thursday as part of measures to respond to the feared Nankai Trough earthquake, which threatens to spawn 30-meter tsunami that could wipe out populous areas of the Pacific coast from central to western Japan in a matter of minutes.

The measures in the interim report, which the Land, Infrastructure, Transport and Tourism Ministry adopted the same day and aims to finalize by March, include a four-step timeline for countering the feared quake.

The e-map would contain detailed geographical data that would be updated with floods, mudslides and other changes as observed from satellites and helicopters, it said. Analysis of “big data” from people’s cellphones and Internet postings will also be used to grasp the movement of evacuees and traffic.

As its first step, the ministry plans to analyze the plains on which the cities of Nagoya and Osaka are situated, given their high populations.

As for the ministry’s response timeline, the report said the government will put priority on protecting lives in the first three hours after the quake, focusing on rescue activities and securing emergency transport routes within 72 hours.

By the time seven to 10 days have passed, it should turn to supporting disaster-affected people while the local governments turn to reconstruction, it said.

Also included is a five-year construction plan to enhance traffic infrastructure in the Yui district of Shizuoka Prefecture, where the Tomei Expressway, the JR Tokaido Line and National Route 1 run parallel to the coast. Since these are the major traffic arteries linking Tokyo to Nagoya, any disruption to the routes would have major implications.

The land ministry will also consider countermeasures for large earthquakes that occur in a series, and strengthening cooperation with police and the Self-Defense Forces in finalizing its report.

The government estimates a Nankai Trough quake would kill up to 323,000 people and cause ¥220 trillion worth of losses under the worst-case scenario.