Earth's tectonic structure imposes strict physical limits on earthquake magnitude, with USGS analyses confirming no fault long enough to produce a moment magnitude 10 event exists or could form. The largest recorded quake reached only 9.5 during the 1960 Valdivia megathrust rupture along Chile's subduction zone, consistent with the longest known fault segments of roughly 1,000 km. Seismological models tie maximum size directly to rupture area and slip, yielding an effective upper bound near 9.5–9.7 under present-day plate boundaries. With just months remaining before 2027, this consensus drives the 99% market-implied probability for "No." Only an improbable global-scale disruption, such as a massive asteroid impact, could theoretically exceed these constraints, though such events fall far outside observed historical or monitoring data.