Japan is spending tens of billions on a shadow capital because a huge earthquake under Tokyo would wreck its economy and shake markets worldwide.

• Scientists put the odds of a massive quake off Japan's coast in the next 30 years at well over half, with damage running past a trillion dollars.
• Tokyo holds most of Japan's big companies, its government, and a third of its people, so one quake takes out almost everything at once.
• The world would feel it fast: Japan still makes most of the special materials used to build computer chips.
• Japanese banks would have to dump their huge pile of American and European stocks and bonds to pay out customers rebuilding their homes, which could crash global markets.
• The backup plan is thin — Osaka is the likely stand-in city, but the fast train linking it to Tokyo won't run until the mid-2030s and most Japanese records are still on paper.

Outlook: The second-capital bill is stuck in parliament and cities are already fighting over the prize, so Japan is burning time it may not have.