USGS M6.1 near Sarabetsu is the first intermediate-depth M6-plus event in our 20-day window
USGS reviewed the 2026-04-26 M6.1 earthquake 18 km west of Sarabetsu, Japan at 81 km depth; in the live USGS warehouse window that begins 2026-04-06, it is the first event in the intermediate-depth / M6-plus bucket.
USGS lists event us6000st1m as a reviewed M6.1 earthquake at 2026-04-26T20:23:55.561Z, 18 km W of Sarabetsu, Japan, with depth 81 km, tsunami = 0, and PAGER alert = green.
The detection here is narrower than a historical claim. In the Zero Day Science USGS warehouse, whose current coverage window starts at 2026-04-06T20:52:43.280Z, this is the first latest-version event whose metadata lands in the (intermediate depth, M6-plus) bucket. The bucket rule is mechanical: intermediate depth means depth_km > 70 and <= 300; M6-plus means magnitude >= 6.0 and < 7.0.
That means the publishable fact is not “largest” or “first ever”. It is that a reviewed USGS event crossed a metadata bucket the live pipeline had not yet seen in its 20-day window, while USGS’s own impact fields remained low-side: no tsunami flag and green PAGER.