As I said, the earthquakes in that drawing were ones which were strongly felt of destructive. For the Japan area that seems to produce a filtering effect which causes those groups of data points to form.

The best database to use for this type of work is probably the dataeqs.txt data file which was previously available at my Web site. I had to reduce the size of the file that is stored there now becasue so many large files were being downloaded from my site that it was shutting down because of bandwidth limitation problems.

A new version of that dataeqs.txt file is almost ready for release. It has been updated with the fatality, injury, and building damage numbers for about 800 earthquakes in the years 1990 through 1999. That update was a LOT or work.

Anyway, the file contains earthquake latitude, longitude, and sun - Earth - moon angle data for more than 20,000 harmless earthquakes plus more than 800 destructive or significant ones for 1990 through 1999 and quite a few of the significant and destructive ones for the years 2000 to the present. So you can use a spreadsheet program such as Excel to choose the earthquake subset you wish and then easily plot them etc.

When time permits I will send you a copy of that updated file and an Excel worksheet page which contains cells which sorts the different data such as angle and fatality values into separate worksheet columns.