33% — Will there be an at least 8.0 magnitude earthquake in California before 2035 Leader: Before 2035 at 33% · Kalshi 33% · 3 contracts · $253 volume · medium confidence Updated 2026-08-24 15:31:16 UTC Tracks the leading outcome in a winner-take-all prediction market set with 3 outcomes. Why this matters: This market estimates a 25% chance of a magnitude 8.0 or greater earthquake striking California before 2035—roughly one in four. The probability reflects scientific uncertainty about major seismic events in a region with active fault lines, particularly the San Andreas Fault system. Historical data shows California has not experienced an 8.0+ magnitude quake in recorded history, which anchors expectations toward the lower end. The near-term contracts (5% for 2027, 14% for 2028) suggest traders view such an event as unlikely in the next 1–2 years but increasingly plausible over a longer window. Key drivers include updated earthquake forecasts from the U.S. Geological Survey, seismic monitoring data showing strain accumulation on major faults, and shifts in scientific consensus about rupture probability. The actual triggering event would be a confirmed 8.0+ magnitude earthquake in California; no scheduled scientific milestones drive near-term resolution. Key factors: - California's largest recorded earthquake was magnitude 7.9 (1906 San Francisco); an 8.0+ would represent a rare, high-energy event relative to historical precedent - USGS publishes updated earthquake hazard models periodically; changes to official fault rupture probability assessments would directly influence market expectations - Seismic monitoring networks detect stress accumulation and fault behavior; sustained changes in measurable strain could shift probability up or down - The time window (2026–2035) is long enough that incremental rupture forecasts and new paleoseismic evidence could substantially revise the baseline estimate - Current 25% headline probability exceeds the year-by-year breakdown (5% by 2027, 14% by 2028), suggesting markets assign non-trivial cumulative risk across years 2028–2035 Contracts: - Will there be an at least 8.0 magnitude earthquake in California before 2035?: Before 2035 — 33¢ Kalshi $26 (weight 10%) - Will there be an at least 8.0 magnitude earthquake in California before 2028?: Before 2028 — 8¢ Kalshi $8 (weight 3%) - Will there be an at least 8 magnitude earthquake in California before 2027?: Before 2027 — 5¢ Kalshi $219 (weight 87%) --- ## Methodology SimpleFunctions aggregates live YES-side prices from Kalshi and Polymarket contracts bound to this question. For binary topics the headline is the liquidity-weighted mid-price (weight = log(1 + 24h volume) × freshness, where freshness is 1.0 if updated <24h, 0.7 if <7d, 0.4 otherwise). For multi-outcome (winner-take-all) topics the headline is the current leader's price — disjoint outcomes are never arithmetically averaged. Snapshots refresh every 5 minutes during market hours. ## SF Signal - SF Index, regime, and 30d Brier calibration are computed separately and surfaced at https://simplefunctions.dev/admin/calibration. - No SimpleFunctions index / regime / calibration signal is bound to this topic yet — the headline above is market-derived only. --- *Last verified: 2026-08-24T15:20:52.878Z* By SimpleFunctions — https://simplefunctions.dev/ Cite as: "33% per prediction markets (SimpleFunctions, August 2026)" Canonical: https://simplefunctions.dev/answer/earthquakecalifornia Full data: https://simplefunctions.dev/api/public/query?q=Will%20there%20be%20an%20at%20least%208.0%20magnitude%20earthquake%20in%20California%20before%202035 Provider: SimpleFunctions — https://simplefunctions.dev