The extreme rarity of magnitude 9.0+ megathrust earthquakes, with none occurring since Japan's 2011 Tohoku event, underpins the 93% market-implied probability against such an event before 2027. USGS records and recurrence models indicate these great earthquakes typically cluster every few decades globally, often separated by 20–50 years on average, and current seismic monitoring shows no elevated activity or precursors at major subduction zones capable of producing them. With only months remaining in the window, the short timeframe further reduces odds despite inherent forecasting uncertainty. A sudden, undetected rupture along zones like Cascadia or southern Chile could theoretically alter outcomes, though such events lack reliable short-term precursors.