Originally posted by FTZ35:

Every 46 minutes there is a 20% chance of an event occuring. Most events can only occur if you are in your base, but there are some that can happen anywhere. There are some that can happen anywhere but those only start later.

I realized that I just don't spend time in my base ever so the attacks never have a chance to spawn. I am always porting to my swamp base and sailing back with Iron nonstop.