Maul does not trigger 2 upheavals from tremor and fury leap-violent upheaval via skull crusher. If this is not intentional to work it is absolutely not clear from tooltips.
It seems only one upheaval is ever cast . I tested this by removing one or the other. and looking at the damage dealt to dummy’s. The double rage cost is payed though. Additionally frenzied onslaught does not trigger on maul either.
The upheaval and maul area that overlaps seem only to count as a single hit for effects from specialisation tree. E.g. Warcry-Berserker only grants one stack despite me expecting (maul + 2x upheaval) 3 stacks. Armor shred effects seem to trigger twice though (as expected assuming one of the upheavals doesn’t happen).
The visual ever shows one upheaval from maul. If looked in to I would suggest for the x2 triggered upheaval to either occur with a delay from one another or so they don’t perfectly overlap looking as if 1 was ever cast . I am aware that damage numbers that happens close to one another are displayed as the sum of both. I accounted for this when testing.