USGS data establish that magnitude 10.0 or larger earthquakes cannot occur because no known fault system on Earth is long enough to release the required energy, with a 10.0 event theoretically needing a rupture spanning roughly 14,000 km. The instrumental record confirms a practical upper bound at 9.5, reached only once in the 1960 Valdivia quake, followed by events such as the 9.2 Alaska 1964 and 9.1 Tōhoku 2011 shocks. Ongoing global monitoring through mid-2026 shows typical M7–8 activity without any trend toward extreme multi-segment failure. With fewer than five months until 2027, the near-certain market odds reflect this geophysical limit; only an unforeseen revision to magnitude scaling relationships or detection of an unknown planetary-scale fault could alter the outcome.