Both spatial and temporal memory unsafety can lead to segfaults, because that's how memory protection is intended to work in the first place. I don't believe it's feasible to write a language that manages to provably never trip a memory protection fault in your typical real-world system, yet still fails to be memory safe, at least in some loose sense. For example, such a language could never be made to execute arbitrary code, because arbitrary code can just trip a segfault. You'd be left with the sort of type confusion logical error that happens all the time anyway in all sorts of "weakly typed" languages - that's not what "memory safety" is about.