起きる and 起こす "to get up", 起きる means "to happen" and other meaning of 起こす is "to lead to / to cause / to produce". We distinguish "transitive and intrastive verbs" very clearly and many verbs have different verbs for them. Besides sometimes one verb has several meanings in Japanese translation but I'll explain about the differences with the basic translation. 起きる is the intransitive verb for "to get up" of "I get up early in the morning". (私は朝早く起きる。) 起こす is the transitive one for "to get (someone) up" of "my dog gets me up early in the morning". (私の犬は朝早く私を起こす。) 起きる is the intransitive verb for "to happen" of "many car accidents happen". (たくさんの自動車事故が起きる。) 起こす is the transitive verb for "to lead to / to cause, to have / to produce / etc" of "many cars have accident". (たくさんの車が事故を起こす。) I hope you get the difference.