USGS assessments and fault mechanics establish the core driver behind the 98.9% market-implied odds against a magnitude 10.0 or larger earthquake before 2027. No known fault system possesses the continuous rupture length of roughly 1,000 miles or more required to release that energy, as each full magnitude step demands about 32 times more energy release than the prior level. The 1960 Valdivia event at 9.5 remains the historical maximum after decades of global monitoring, with 2026 activity limited to events around 7.8 or below. While seismic models carry inherent uncertainty and new observations could theoretically revise fault-length estimates, current tectonic configurations and observational records provide no credible pathway to such an extreme outcome within the timeframe.