The verb 裂ける means to be torn. I know it's intransitive. but shouldn't it be translated as to tear? what's the difference between 裂ける and 裂けている? both of them are in the state of being torn? shouldn't 裂ける be in the state of being on the verge or in the process of being torn?
裂ける does mean “to tear” in its intransitive sense. Like the English verb, it doesn’t refer to a lasting state but either an instantaneous change (“to come apart”) or a static property (“to be tearable”). 裂けている describes either a resulting state (“to be torn”) or an ongoing change (“to be coming apart”).