I occasionally see a global pop up saying something like "Mr. Y killed a whatsit worth 27 PED at Arkadia Event Area 2". Where the heck are the event areas? They aren't on the map.
You have to visit them first to get them on map. The easiest way - open you Event Register, find one of the areas in the list on the left and click the сompass sign on the right, the location will be shown on the map (only once, won't stay on your map). Set a marker and go there. Repeat for every area.