You've pointed at the most provocative mainstream tidal-triggering work. Sachiko Tanaka, the author of the cited work, is our co-author on our Science triggering paper.

Briefly, the idea is that the earthquakes may correlate with the tides better just before big earthquakes. So the correlation itself has little predictive value, but when the correlation increases might be a danger signal.

The idea has been around for years, the Chinese LURR theory is similar, but so far the data supporting the theory is thin.