A burrowing attack ignored my artillery, tunneled across an entire ocean and into my solar fields. How do I defend against it?

The turrets cause underground attacks to dig out in about a 15 tile radius of them.
Additionally, normal underground attacks will not attack through multiple chunks of water. This can only happen in response to the use of artillery
Thus, before using artillery, you need to protect vulnerabilities or be prepared to deal with an underground attack personally

i reset my evolution factor to 0 shortly after underground attacks appeared. but they still appear! not very often... i'll disable the setting until evolution reaches 0.4 again, but this is something i didn't expect to happen

probably you didn't expect me to play in a way where the biter settings are Too Hard and i reset evolution sometimes

Once appeared, the chance of underground attacks will never drop below 0.01%.
However, I think this is a fairly low probability. Especially considering that they do not attack through several chunks of water, and the strength of the squad with low evolution is also insignificant

So far I don't see the need to change this

it did make for an unpleasant surprise, which is kind of what fun rampant is for <3