US, Japan rehearse their response to feared Nankai Trough megaquake

YOKOTA AIR BASE, Japan — U.S. and Japanese forces are rehearsing their response to a catastrophic Nankai Trough earthquake this week, testing how the allies would coordinate relief efforts during a disaster scientists say has a high probability of striking within the next three decades.

Joint Exercise Rescue 2026 began Tuesday and runs through Friday at Yokota and Camp Ichigaya, headquarters of Japan’s Ministry of Defense in Tokyo.

The command post training simulates a magnitude-8 to -9 earthquake along the Nankai Trough and a tsunami striking southern and central Japan, according to a U.S. Forces Japan news release Wednesday.

The Nankai Trough is a tectonic plate boundary stretching off Japan’s Pacific coast from central Honshu to Kyushu. Japan’s Earthquake Research Committee estimates a 70% to 80% chance of a magnitude-8 to -9 quake there within the next 30 years.

The exercise comes as USFJ shifts from a headquarters focused primarily on liaison duties to a more operational command working alongside Japan’s new Joint Operations Command, which was established last year to better coordinate the country’s military services.

About 100 U.S. personnel are participating in the training, USFJ spokesman Air Force Col. John Severns said by email Wednesday.

The scenarios echoes Operation Tomodachi, the massive U.S.-Japan humanitarian mission launched after the magnitude-9 earthquake and tsunami that struck northeastern Japan on March 11, 2011. The disaster killed nearly 20,000 people and triggered the Fukushima Daiichi nuclear meltdown.

U.S. forces have also supported Japan after more recent natural disasters, including the 2024 Noto Peninsula earthquake, when Army helicopters delivered thousands of pounds of relief supplies, and the 2016 Kumamoto earthquakes, when U.S. aircraft airlifted emergency aid to affected communities.

During the exercise, U.S. and Japanese personnel will rehearse logistics, medical support, evacuation coordination and life-support operations while responding to requests from the Japanese government.

“Joint Exercise Rescue is an opportunity for U.S. Forces Japan and JJOC to stress-test our coordination mechanisms and ensure that, in the event of a real-world catastrophe, our bilateral response is rapid, seamless, and effective,” Air Force Col. Mark Schulman, USFJ’s exercise director, said in the release.

The drills also include simulated bilateral press conferences and other crisis communications to ensure U.S. and Japanese officials can deliver coordinated information during a major disaster.