It has taken me several hours of work spread over a few days, but I just added a chart to the Terral Croft page showing that there is no 188-day cycle as he has claimed. The chart shows the total seismic energy (taking into account everything above 6.0) in joules for the period. I converted this data using the formula relating Magnitude to Joules: $E = 10^{1.44×Ms +5.24}$, where Ms is the surface magnitude. I found this formula on a web page at the University of Alaska. I found other formula elsewhere, notably $E = 10^{1.5×R + 4.8}$ at the Earthquake Power Converter, which yields similar results.

This is based on a query of the USGS database, the results of which are attached to the page. Anybody can query the database at http://earthquake.usgs.gov/earthquakes/eqarchives/epic/