Did you check "gamecore\debris"? The source makes reference to the following:
_part_initexploders:
`
rem Load spark, fire and smoke
tfile$="gamecore\debris\spark.tga" : explodedecalspark=loadinternalimagecompressquality(tfile$,5,1)
tfile$="gamecore\debris\fire.tga" : explodedecalfire=loadinternalimagecompressquality(tfile$,5,1)
tfile$="gamecore\debris\smoke.tga" : explodedecalsmoke=loadinternalimagecompressquality(tfile$,5,1)
tfile$="gamecore\debris\scorched.tga" : explosionscorch=loadinternalimagecompressquality(tfile$,5,1)
tfile$="gamecore\debris\stressed.tga" : explosionstressed=loadinternalimagecompressquality(tfile$,5,1)
`
I had assumed this was where the "explosions" were referenced, but I could be incorrect.

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