Monthly phase rotations gave no clear daily cycle in global shallow M5.5+ earthquakes in 2000-2025

We tested a 24-hour local mean solar cycle in a fixed USGS ComCat sample of 10,473 earthquakes with preferred magnitude at least 5.5 and depth at most 70 km in 2000-2025. The fitted first harmonic amplitude was 3.85%. An independent-event test gave p = 0.0208. A test that rotated each complete month as one group gave p = 0.19575. Its null root mean square amplitude was 53.3% larger than the independent-event value. Weekly and yearly rotations also gave p above 0.1. The noon harmonic coefficient was +0.17%, with a conditional 95% year resampling interval of -2.52% to +2.80%. These tests do not resolve a common daily cycle. They do not exclude local effects or identify a physical cause. Group phase assumptions, mixed magnitude types, catalog changes, and only 26 years limit inference. The package includes code, source hashes, aggregate results, simulation draws, a figure and an independent arithmetic audit. Raw external records remain outside the package.

earthquake timing · local solar time · daily cycle · phase rotation · event dependence · ComCat · null result