Tools chosen: kalshi_direct kalshi_related polymarket_related wikipedia claude_news gdelt_news code_execution

Sub-questions (Fermi decomposition)

Planner reasoning

This is fundamentally a base-rate (Poisson) question: how often do M≥8.0 earthquakes occur with epicenters in/near Japan, scaled to the remaining window until Jan 1, 2030. The key research tasks are anchoring on the Kalshi price, establishing the historical frequency from catalog data (USGS/JMA), and clarifying the geographic restriction ('Japan or its territorial waters'), which excludes many offshore trench events and materially lowers the rate.

# Current state Resolution requires at least one M≥8.0 earthquake epicentered in Japan or its territorial waters before 2030-01-01. No qualifying event has occurred since the 2011 Tōhoku M9.1; current hazard sits on official 30-year subduction-zone probability estimates (Nankai Trough, Japan Trench, Kuril Trench), not on any confirmed near-term rupture. Kalshi YES currently prices this at 40%, down sharply from a 77% high. # Timeline of key events - 1900–2011: historical record shows ~7–10 M≥8.0 events in/near Japan (1896 Sanriku M8.5, 1933 Sanriku M8.4, 1952/1968/2003 Tokachi-oki M8+, 1994 Hokkaido M8.2, 2011 Tōhoku M9.1) — confirmed (Wikipedia/volcanodiscovery). - 2011-03-11: Tōhoku M9.0–9.1 earthquake/tsunami, most powerful on record in Japan — confirmed (Wikipedia). - 2024-01-01: M7.5 Noto Peninsula earthquake, largest of 2024 but below threshold — confirmed (claude_news/Wikipedia). - 2024-08-08: M7.1 Kōchi earthquake triggers JMA's first-ever Nankai Trough "massive earthquake" advisory — confirmed (nippon.com). - 2025-01-15: ERC raises 30-year Nankai Trough M8-9 probability to "around 80%" (from 74-81%/75-82%) — confirmed (nippon.com/Fortune). - 2025-09-27: ERC methodological revision widens 30-year Nankai probability range to 60–94.5%+ (alt. model: 20–50%) — confirmed (Japan Times). - 2025 (undated): New HERP research group formed for Kuril Trench M9-class imminent-event contingency planning — reported (Fuji Press). - ~2026-04 (implied): Aggregator (Octagon AI) reports a volatility spike in this Kalshi market, price range historically 46–66% before recent decline to ~40-47% — reported, unverified source. - 2026-07-29/30: Widespread news coverage on "why Japan has so many large earthquakes," tied to a Kumamoto-area quake event — reported (CNN/Asahi/AP-syndicated); magnitude not specified as ≥8.0 in retrieved snippets. # Event Will an earthquake of magnitude ≥8.0 with epicenter in Japan or its territorial waters occur before 2030-01-01? # Outcomes to forecast Yes / No # Kalshi market anchor KXEARTHQUAKEJAPAN-30 current YES price: **40.00%**. 7-day change: -5pp; 30-day change: -25pp (sharp decline from recent highs). Range over ~148 days: 31%–77%. Avg daily volume ~177-269 contracts (moderate liquidity). The 30-day plunge from ~65-77% down to 40% suggests a de-risking event or reassessment, not a resolution — no qualifying earthquake has occurred, so this is a pure repricing of probability, not new information about outcome. # Sub-question answers 1. **Kalshi price/history** — Current YES = 40%; recently traded as high as 77%, low 31%, with a steep -25pp 30-day drop (kalshi_direct). Third-party aggregator (Octagon AI, unverified) claims historical range 46-66% and a "volatility spike" around April 2026. 2. **Historical M≥8.0 rate since 1900/1950** — ~9-10 events M8.0-9.1 since 1900 per volcanodiscovery.com; commonly cited defensible count is 7-9 "in/near Japan" events, implying λ≈0.056-0.08/yr. No M8+ since 2011. 3. **Territorial-waters restriction effect** — Not explicitly quantified in research; broader "Japan region" USGS catalogs (including Bonin/Ogasawara deep events, far Kuril arc) would count more events than the stricter "epicenter in Japan/territorial waters" wording. This likely trims the historical count toward the lower end (~5-8) versus broader regional catalogs (~9-10). 4. **Official ERC probability** — Nankai Trough M8-9: 30-year probability revised 2025-09 to 60-94.5%+ (or 20-50% under alt. model), up from "~80%" in Jan 2025. Japan Trench M7-8: >90% (30yr, 2019 estimate). Kuril/Chishima Trench: up to 80% for M>7.8, 7-40% for M>8.8 (30yr) (Springer/HERP). 5. **Recent advisories/swarms** — Aug 2024 Kōchi M7.1 triggered first-ever Nankai "massive earthquake" advisory; 2025 saw new HERP Kuril Trench contingency-planning group. No confirmed 2025-Tokara/Aomori swarm detail retrieved; 2026-07 Kumamoto-area quake generated heavy news coverage but magnitude not confirmed ≥8.0. 6. **Poisson-implied probability** — Using λ≈0.06-0.08/yr and remaining time to 2030 (research assumed ~4.6yr from mid-2025; actual "now" appears to be mid/late-2026 per GDELT dates, giving ~3.4yr remaining), P(≥1)≈19-28% (code_execution model, adjusted). This sits well below the current 40% Kalshi price. # Key facts (high-confidence, factual) 1. [volcanodiscovery.com] ~9-10 M≥8.0 events in/near Japan since 1900; none since 2011. 2. [Japan Times, 2025-09-27] ERC 30-year Nankai Trough M8-9 probability: 60-94.5%+ (new model) or 20-50% (alt. model). 3. [nippon.com] Aug 2024 Kōchi M7.1 triggered JMA's first Nankai "massive earthquake" advisory. 4. [Kalshi] YES price 40%, down 25pp in 30 days from a 77% high. # Cross-market signals - Kalshi related: KXEARTHQUAKECALIFORNIA-35 at 48% (+22% 30d, rising); KXEARTHQUAKECALIFORNIA-28 at 14% (flat) — different hazard base rates, limited direct arbitrage relevance. - Polymarket: no matching markets found (0/100 scanned). - Sportsbook implied: N/A (not applicable to this category). # Analyst opinions and speculation - claude_news/Octagon AI (unverified aggregator) suggests market has been volatile, implying trader uncertainty/overreaction to news events (e.g., Aug 2024 advisory, 2026 Kumamoto coverage) rather than fundamental base-rate shifts. - HERP chair Naoshi Hirata (2025): "a major quake could occur at any time" — official language emphasizing near-term uncertainty, not a specific short-window forecast. # Directional lean per outcome - **Yes**: Elevated official 30-year Nankai/Japan Trench/Kuril probabilities (60-94%+ over 30yr) create long-run tail risk; Japan sits on multiple active megathrust systems; recent advisories (2024) show elevated concern. - **No**: Poisson base-rate model (λ from 125yr history) implies only ~19-28% for the ~3.5-4.5yr window remaining — well below Kalshi's 40% price. No M8+ event since 2011 (14+ year quiet period). Official 30yr probabilities are for 30-year windows, not the ~4yr window this market covers, so naive application overstates near-term risk. # Gaps / unknowns - Exact current date unclear (GDELT shows 2026-07 news; code_execution assumed "today"=2025-06-01), materially affecting remaining-time calculation and thus true Poisson probability — should be recalculated with correct current date (~3.2-3.5 yrs remaining likely). - No clear quantification of how "territorial waters" wording narrows historical event count vs. broader USGS "Japan region." - Unverified whether 2026-07 Kumamoto earthquake reached M8.0 (coverage suggests notable but magnitude not confirmed ≥8.0 in snippets). - Cause of 30-day Kalshi price drop (-25pp) not explained by retrieved news — may reflect trader repricing after passage of time without event, or an unreported market-specific development. # Calibration anchors - Kalshi current YES price: 40% (anchor). - Poisson base-rate model: ~19-28% (adjusted for likely current date). - Official ERC 30-year Nankai probability (60-94.5%) is for a longer window (30yr vs ~3.5-4.5yr here) — not directly comparable without time-scaling. - Precedent: no M8+ Japan event in 14+ years since 2011 despite elevated official hazard estimates throughout that period.

1. Both forecasters lean heavily on the naive historical Poisson rate (λ≈0.06-0.08/yr) but never reconcile it with the ERC's own 30-year Nankai-only probability (60-94.5%), which annualizes to roughly λ≈0.03-0.11/yr for Nankai alone — comparable to or exceeding the "all Japan" historical rate. This suggests the historical base rate may be stale/too low given specifically elevated current subduction-zone risk, yet neither forecast attempts this cross-check. 2. Neither forecast grapples with the brief's flagged possibility that Nankai, Japan Trench, and Kuril are largely independent hazard sources whose probabilities should combine (1-∏(1-p_i)) rather than being folded into one blended historical λ; treating them as a single Poisson process likely understates aggregate risk from multiple active megathrusts. 3. The unexplained -25pp Kalshi price drop over 30 days is dismissed by both as "residual retail overpricing correction," but the brief explicitly flags this as unexplained by any retrieved news — it could instead reflect informed trader repositioning or a market-structure effect, and neither forecast weighs the alternative hypothesis that the market may hold information they lack. 4. Both forecasts substantially undercut the Kalshi anchor (40%) by 6-13pp with only moderate confidence (0.56 each), despite Kalshi being a moderately liquid, real-money market; this is a fairly large deviation from the price anchor without a correspondingly decisive evidentiary edge, especially given how wide the calibration range (19-40%) already is. 5. Neither forecast addresses potential aftershock/triggering clustering dynamics (e.g., 2024 Kōchi M7.1 triggering the first-ever Nankai advisory) that would violate the constant-rate Poisson assumption and could elevate near-term hazard above the flat historical average, a scenario the brief's advisory/swarm evidence hints at but the models ignore. 6. The "territorial waters" restriction is acknowledged as unquantified and could trim the historical event count to ~5-8 (vs. 9-10), which would lower Forecast 2's implicit base rate further, yet Forecast 2 assigns more weight to Yes (34%) than Forecast 1 without explaining why it discounted this narrowing effect less.

30% (56% confidence)

Yes: 30% No: 70%

The cleanest quantitative anchor is the historical rate of ~7-10 M≥8.0 events in/near Japan since 1900 (λ≈0.06-0.08/yr), which over the ~3.3-3.5 years remaining to 2030 implies only ~19-25%. The devil's advocate is right that time-dependent ERC models for Nankai alone (60-94.5% over 30 years) and the combination of independent Japan Trench/Kuril sources could push effective near-term hazard above the flat historical average, and that a moderately liquid real-money market at 40% deserves respect even if its -25pp slide is unexplained; that argues against slicing all the way down to the naive Poisson figure. Offsetting this, the strict 'epicenter in Japan/territorial waters' wording likely trims the qualifying historical count, 14+ years have passed since 2011 without a qualifying event despite continuously elevated official estimates, and disaster/catastrophe markets on retail venues systematically trade above base rates. I therefore land at ~30% for Yes — modestly below the Kalshi anchor but above the pure base-rate model, reflecting genuine uncertainty about multi-source and clustering effects.

Total pipeline time: 305.5s