“the debris within the well appears to have come from cleanup efforts after a destructive earthquake”
I’m failing to imagine any circumstance where throwing corpses into the well you get drinking water from constitutes a “cleanup effort”.
Probably a manpower shortage — most of the population was killed or buried in rubble and debris, and here’s this handy pre-dug hole...
Could also have been the entire population was wiped out, and the smell was carrying downwind to a neighboring village that had better fortune.