OSAKA (Kyodo) -- With the World Exposition in Osaka to be held on an artificial island, concerns have risen over the possibility of visitors becoming stranded if a disaster cuts off all three routes to the venue.

Organizers are stockpiling supplies to prepare for a scenario where evacuation from Yumeshima could take up to three days. According to new projections released March 31 for a megaquake in the Nankai Trough, the area where the artificial island is located could experience temblors as strong as upper 6 on the Japanese seismic intensity scale of 7.

The Osaka prefectural government estimates that tsunami waves as high as 5.4 meters could hit the venue, but flooding is expected to be limited to the island's outer edges given the venue sits 11 meters above sea level.

Prompt evacuation, however, may prove impossible as access to the venue is limited to a bridge, a tunnel, and a subway. In the event they are temporarily closed for safety checks, visitors would also be unable to leave on foot.

On peak days, over 220,000 people are expected to visit the six-month-long global event starting Sunday. Organizers have therefore stockpiled 600,000 meals, 1.9 million bottles of drinking water, 1.95 million portable toilet kits, and other emergency supplies to last for 72 hours.

National pavilions, event facilities, rest areas, and the Grand Ring, a vast wooden roof encircling the pavilions, are set to be used as temporary shelters if necessary.

Helicopters or boats will be used to transport any sick and wounded off the island while access remains cut off. In January, a large-scale drill involving Self-Defense Forces and police was conducted on a neighboring island, simulating delivering relief supplies and evacuating individuals by air and sea during a major earthquake.

"It is essential to be prepared for any scenario to ensure we welcome visitors with a thorough and safe system in place," said a senior official of the Japan Association for the 2025 World Exposition.