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What if a great earthquake and tsunami hit Japan?

Japan builds about 8.9% of the world's motor vehicles — and 2011's M9.0 shaved nearly half a point off US GDP through supply chains alone. Sole-source suppliers, not assembly plants, were the binding constraint. Model the shock yourself.

1The setup

Japan built 8.23M motor vehicles in 2024 out of 92.7M worldwide — about 8.9% of world production, second only to China — and Toyota alone leads all automaker groups. The 2011 Tōhoku quake (M9.0) plus tsunami is the benchmark supply-chain disaster: Japan's GDP shrank 0.9% in Q1 2011, the IMF cut its full-year forecast from +1.4% to −0.7%, and the US Federal Reserve's post-mortem found the disaster shaved nearly 0.5 percentage points off US Q2 2011 GDP. The recovery took roughly 5 months, with Toyota expecting Asia-Oceania normalization only in Aug–Sep 2011. The lesson of 2011: the binding constraint was not the assembly plants but sole-source electronics and chemical suppliers that could not be quickly resourced. A smaller M7.5–7.9 shock stays inside the plant-damage register; the top band models the Tōhoku-scale cascade on purpose.

Market check · Polymarket

What the market thinks

Where will a 6.0+ magnitude earthquake occur by end of September?

Polymarket · live contract

28%

implied chance of “Yes” on a 6.0+ magnitude earthquake occur in Japan this month…

The market says 28% — you say the real chance is…

Your take lives on this device only. Illustrative — not a bet, not advice.

Closest live contract — whether a 6.0+ quake hits Japan within the calendar month, on a monthly clock. It is not a forecast of a great quake or tsunami, and it is not a contract on Japanese equities. Thin market — few traders; small bets move these odds.

$4.4K traded · resolves by 2026-10-04Odds as of Sep 21, 2026View this market on Polymarket →

Illustrative only — not financial advice, not a recommendation.

2Right now

autos

INCOMPLETE

Coverage incomplete — the monitor is missing feeds for autos, so no score is shown. Incomplete coverage is not zero risk.

Monitor data as of Sep 24, 2026. Scores are observed readings, not forecasts.

How the shock travels

Assembly plants and power

Plants in the disaster zone close directly and rolling blackouts compound the outage: in April 2011 Toyota's global output fell 48.1% YoY and Honda's 52.9%, with nuclear shutdowns making power the binding constraint beyond plant damage.

Evidence: IndustryWeek on April 2011 output + CRS R41831 — Toyota −48.1%, Honda −52.9% global output; rolling blackouts compounded plant damage

Sole-source supplier chokepoints

Disaster-region makers of automotive electronics and specialty chemicals were 'not easily available elsewhere' — they kept plants below capacity after physical repairs were done and hit US plants weeks later.

Evidence: CRS R41831 — sole-source parts and chemicals not quickly substitutable; overseas plants slowed within weeks

Port disruption

Japan's auto exports concentrate at Nagoya, Tokyo, and Yokohama — the largest and biggest car-export ports — so a tsunami-damaged port throttles exports regardless of how fast plants recover.

Evidence: Nagoya Port Authority + JIFFA/MLIT throughput data — container and auto exports concentrate at three ports

Caveat: 2011 port-outage duration is UNVERIFIED — the exposure is structural, not measured

Overseas-plant knock-ons

As Japan-sourced parts ran short, Toyota suspended North American overtime, GM briefly shut a Louisiana plant, and Honda's Mexico plant considered furloughs — the supply chain transmits the shock across the Pacific.

Evidence: ScienceDaily/InvestorPlace on 2011 — US and Mexico assembly slowed for lack of Japan-sourced parts

Consumer prices

ALG measured +3–6% US transaction-price increases for affected models after Japanese vehicle production fell to roughly 40% of prior-year levels — the terminal demand-side link.

Evidence: ALG via AutoBlog — +3–6% transaction prices on affected models, 2011

3The exposure

Coverage incomplete — the monitor does not track exporter shares for autos. The exposure for this scenario is sized from the declared capacity snapshot in the “Adjust the assumptions” section below instead.

Trade map

Who ships it, who can’t do without it

2024 vintage · annual data, 1–2y lag

Sourced trade structure — the scenario’s shock geography at country resolution. Exposure, not a forecast.

Autos · Japan

Top exporters

  • Germany

    17.36% of world exports

  • Japan

    12.26% of world exports

  • China

    9.13% of world exports

  • South Korea

    7.31% of world exports

  • Mexico

    7.03% of world exports

Note: HS 8703 motor cars and other motor vehicles principally designed for the transport of persons, incl. station wagons and racing cars (BACI 2024). Commercial vehicles (8704), parts (8708) excluded.

Exposed importers

Shocked exporters: Japan

Japanese auto export ports

via Nagoya / Tokyo / Yokohama ports (no single strait or canal)

No single corridor — share not applicable — Auto exports load at Nagoya / Tokyo / Yokohama ports; no single strait or canal. No route share applies -- this is not missing research.

How we map this

Exporter and importer shares are 2024 vintage · annual data, 1–2y lag from UN Comtrade and OEC (BACI/CEPII); an importer counts as exposed when ≥20% of its autos imports come from a shocked exporter. The shock geography is the scenario’s own focus selection. Annual data with a 1–2 year reporting lag — the structure moves slowly, the prices don’t.

4Adjust the assumptions

Earthquake magnitudeM9.0+

Historical check: No autos episode on record — no historical range to compare this setting against.

What share of the exposed capacity is disrupted.

Resolution: Moment magnitude reported by the USGS

Share of world motor-vehicle production in the hazard zone

World motor-vehicle production (Japan) — 8.9% of world motor-vehicle production

Exposed under your assumptions: 8.0% (8.9% × 90% severity)

The hatched area is modeled from your assumptions, not a measured outcome.

Source: JAMA/OICA 2024 (Japan 8.23M of 92.7M vehicles)

Exposed ≠ lost — affected trade can reroute, draw stocks, or substitute. This sizes the exposure, not the damage.

150d

Historical check: No autos episode on record — no historical range to compare this setting against.

Resolution: Days until Japanese auto output returns to pre-quake levels (JAMA monthly statistics) — 2011 took ~5 months

60d

Your assumption — not a measured buffer.

Resolution: Assumed days of stockpile cover — an assumption, not a measured buffer

Disruption timeline
090180270365 days
Disruption: 150 days
Assumed cover: 60 days — your assumptionYour assumption

90 days buyers can't ride out — not automatically a physical shortage

What this would have meant

At these settings, about 8.0% of the world's autos exports would be exposed to the disruption, and the disruption runs 150 days against 60 days of assumed stockpile cover, leaving about 90 days beyond what the assumed stockpile covers.

No close historical match in our records — this scenario is outside our recorded experience.

What this assumes
  • Exposure: Target share 8.9% × severity 90% = 8.0% exposed.
  • Uncovered days: max(0, 150 − 60) = 90.
  • Exposed ≠ lost: affected trade can reroute, draw down stocks, or find substitutes — this number sizes the exposure, not the damage.
  • Exporter share ≠ spare capacity: rivals may not be able to surge supply to fill the gap.
  • Stockpile cover of 60 days is your assumption, not a measured buffer.
  • Results are physical-exposure arithmetic from your stated assumptions — not a price forecast.

Analog check

No close historical match in our records — this scenario is outside our recorded experience.

Want the full controls? Reopen autos on its commodity page.

5What happened before

For perspective, not prediction

What to watch

  • USGS magnitude and tsunami assessment — the top band models the 2011 Tōhoku M9.0 scale
  • JAMA monthly domestic production — the grading line is ≥20% down YoY in any month within 90 days
  • Which assembly plants and supplier clusters report damage — in 2011 the sole-source tier was the binding constraint
  • Port of Nagoya, Tokyo, and Yokohama status — container and car-export throughput concentration
  • US dealer inventory and transaction-price reports for Japan-built models

Curated by Morrowfly — these are things to check, not monitor conditions.

Make it yours

Your call, in your words — recorded privately on this device, with a check-back in 30, 60, or 90 days.

Tell us

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Read by a human · never auto-published

Illustrative scenario. Not a prediction. Not financial advice.

Monitor data as of Sep 24, 2026 · Trade vintage 2024 · Scoring v3.2

What if a great earthquake and tsunami hit Japan? | Morrowfly