Onikakushi-hen: It isn't mentioned whether Rika dies or not.
Watanagashi-hen: Rika commits suicide (in the anime; I think she's killed by Shion in the game), the Disaster does not occur.
Tatarigoroshi-hen: Rika is killed at the shrine, and the Disaster occurs.
Himatsubushi-hen: Rika is killed, and the Disaster occurs.
Meakashi-hen: Same as Watanagashi-hen (in the anime; the game differs slightly), Rika dies but the disaster does not occur.
Tsumihoroboshi-hen: Rika's death is not shown, nor is the great disaster. You would have known from the ending though that the disaster did occur (or else there wouldn't be a need for a reboot).
The only time the disaster does not occur is in the Watanagashi/Meakashi arcs. I kinda forgot about that and made the assumption that the disaster occurs whenever she is killed. My apologies
I've been vaguely spoiled by the tips and discussions at ASuki, but am still looking forward to Higurashi 2nd nonetheless
