One-minute magnitude similarity remains under an hour-and-area shuffle for Ridgecrest events on days 1 to 30

We tested a published short-gap magnitude pattern in a fixed USGS Ridgecrest catalog. The sample has 931 events with preferred magnitude at least 2.5 on days 1 to 30 after the 2019 M7.1 event. It has 98 adjacent pairs with gaps of at most one minute. Their mean absolute magnitude difference is 0.3415. A shuffle within hour, preferred magnitude type, and 10 km square gives an exact mean of 0.3912. None of 19,999 draws is as low as the observation; the lower-tail Monte Carlo p value is 0.00005. The excess similarity is 57.2% smaller than under a day-and-type shuffle. All six planned checks retain a lower-tail departure. Only 51 of 98 pair scores can vary under the primary shuffle. This is a conditional catalog result from a selected follow-up. It does not identify physical magnitude memory or separate missed events, rapid local changes, and measurement effects. The package gives fixed source bytes, source hashes, pair evidence, code, all shuffle scores, an exact-mean audit, a figure, and a successful offline repeat.

Ridgecrest · magnitude similarity · conditional permutation · catalog incompleteness · spatial mixture · reproducibility