How to stop receiving Calendar alerts

I use Fantastical on my Mac instead of Calendar, but Fantastical can only sync with my Google Calendar via the Mac Calendar, so I have to sync Calendar with Google. I get daily email alerts directly from the Google Calendar about events, but I also get duplicate email alerts via Calendar.

I have alerts turned off in Calendar, but yet they show up in the Notification Center...and I have Calendar set to NONE in Preferences|Notification Center, so I shouldn't be receiving the dupicate alerts. FWIW, the duplicate alerts started appearing only when I added Google Calendar to the Mac Calendar.