Buying property in Japan: disaster-risk due diligence, in English

Japan manages natural-hazard risk better than almost anywhere — and publishes remarkably detailed data about it. The catch: it is almost all in Japanese. This guide covers what to check before you buy, and what the numbers mean.

Reference information, not investment or insurance advice. Sources: MLIT/GSI, J-SHIS (NIED).

The six hazards worth checking for any address

Flood (river overflow — depth and how long water stays), earthquake (probability of strong shaking and how the local ground amplifies it), landslide (designated hazard areas), tsunami, storm surge (typhoon-driven sea rise), and liquefaction (loose, sandy ground behaving like liquid during shaking). All six are published as official government data; each varies dramatically within a single city.

Reading earthquake numbers: shindo and the 30-year probability

Japan measures shaking with the JMA intensity scale (shindo), not magnitude. For property decisions, shindo 6-lower is the key threshold: shaking at which you cannot stay standing and buildings with poor earthquake resistance can collapse. Official probabilities are stated over 30 years — conveniently, about the length of a mortgage. As a verified example, a point in eastern Tokyo (Oshiage, Sumida) shows an 83.2% chance of shindo 6-lower or stronger within 30 years. At that level, the realistic reading is: plan for it to happen while you own the property. A low number, however, is not a guarantee — before the 2016 Kumamoto earthquake, the equivalent figure there was in the single digits.

Two building facts do most of the protective work: the post-1981 "new seismic standard" (shin-taishin), and, for houses, the geotechnical survey report.

Liquefaction: the quiet deal-changer

On reclaimed land, former river channels and drained lowland, shaking can make the ground itself fail — buildings tilt, pipes break. Two things foreign buyers often learn too late: liquefaction damage is not covered by fire insurance; only earthquake insurance covers it, and for detached houses, countermeasures (pile foundations, ground improvement) should be confirmed in writing before purchase.

The disclosure your agent must give you

Since 2020, Japanese real-estate agents are legally required to explain the flood hazard map for the property during the pre-contract disclosure (jūyō jikō setsumei). Ask for it explicitly, and check that what you hear matches the official data — an independent check takes minutes and removes the language-barrier risk.

A practical pre-purchase checklist

① Check all six hazards for the exact address (not the neighborhood's reputation). ② Match the agent's hazard-map disclosure against official data. ③ For flood-assumed land: foundation height, and where the water heater/electrical equipment sit. ④ Request the geotechnical report. ⑤ Confirm new-seismic-standard compliance. ⑥ Get fire (+flood coverage) and earthquake insurance quotes before committing — the premium itself tells you how insurers price the location's risk.

Check any address now

mamoie's free checker runs all six hazards for any Japanese address from official data (UI in Japanese — paste any address). Developers and platforms can use the free English API.

mamoie (EN)　|　Tokyo flood risk　|　Data sources　|　Operated by civilrize