**A 5.3-magnitude earthquake near Yōkaichiba, Japan, on October 1, 2026, registered as the day's largest event according to USGS and multiple global seismic networks, driving the market's 98.5% implied probability on the 5.3–5.4 bin.** Official catalogs list no higher-magnitude quakes that day, with secondary events reaching only 5.2 in Afghanistan and 5.1 clusters in the Solomon Islands and elsewhere. This outcome aligns with typical daily global maxima under current seismic conditions, where M5+ events occur regularly but larger ones remain infrequent without specific tectonic triggers. Revised magnitude assessments or unreported late events could theoretically shift resolution, though cross-agency confirmation makes such adjustments improbable.