In this thread Quercus found out the general extension and strength of the auras on the island and it's surroundings.
https://forum.atlas-games.com/t/chapter-1c-chasing-the-sounds-of-magic/8453/17
The aura around the tree is 3. There are equally strong auras around the pillars that rises out of the sea some five miles north of the island. We haven't been able to examine them closer yet.