The word "劈里啪啦" is formed as an onomatopoeic compound through phonetic reduplication, where the characters are paired based on sound similarity: "劈" (pī) and "啪" (pā) share the initial 'p' sound, while "里" (lǐ) and "啦" (lā) share the initial 'l' sound, creating an alternating consonant pattern that mimics repetitive crackling or popping noises.