Even then, nobody knew about Lavos.
As for knowing about Lavos? The Arris Directer knew.
The Arris Director knew.
Director: ......
Lavos......
I seriously doubt the Director knew about Lavos, what the being actually is, what it did to Zeal, the fact that it landed.
The Director saw Lavos on the screen, so from all facts known about the word and how it was handed down, most likely he saw that it was big, and shot fire. So he could easily, like Ayla, call it Lavos aka "Big Fire". There is no evidence to suggest that they understand or know what a Lavos is. Heck, only in 2300AD does it seem that anyone knew what Lavos was.
[Monitor]
2300 A.D.
Lithosphere Investigation Report
~
~
- Report no. 27 -
~
[Unknown Life Force,
Parasitic to the Planet]
Geologic Stratum Result - 65,000,000 B.C.
Code - '"Lavos"'
Not only is this in CC, but the report was made in 2300AD, and is the 27th report.
So a computer must have been monitoring it since 1999AD I guess :/ Since the Day of Lavos.
While it's kind of off-topic, I can't help but post a link to DBoruta's theory about the Ocean Palace incident. According to that theory, Lavos would have manipulated Queen Zeal into bringing the Mammon Machine close to him so that he could claim back the Frozen Flame.
Ah, yes, that theory...well, while we have no real evidence the Frozen Flame was actually the central core of the Mammon Machine(apart from Radical Dreamers which was rendered non-canon, though the fact that it does occur in an alternate universe suggests that it is possible--and potentially likely, given the simularities between the universes--that the Frozen Flame was thus the core of the Keystone Mammon Machine) it's certainly possible. In fact, it could work together with what I suggest, since having the Frozen Flame would easily help with empowering Lavos in some fashion.
I brought this up earlier in a post 2 years ago. We can just connect the dots with RD and CC, and it all fits together. Schala is pretty much an arbiter, able to control the Mammon Machine. The Mammon Machine has the flame in it. The Mammon Machine is brought closer to Lavos, who awakens in it's presence for any reason (Maybe it wants to take it back and become powerful or something?). This both happened in CT and RD (just without the flame being mentioned in CT) and is a motif in CC with the flame being the medium to evolve Lavos with an arbiter.
CT also supports a premature version of the Flame, with Belthasar stating that in 3,000,000BC, humans changed forever when they made contact with a red shard (the flame). So we can assume that back in 1996, the Flame concept wasn't fully designed, and they fully integrated it in CC and kind of added the background of it in RD.
Interesting concept :O
Oh and to Kyronea, just to go back to another point:
Whilst I was digging through the script in CT, the Arris Dome Director tells people to head off to the "ShelterDomes". So it's plausible that many more than 100 people survived, probably a lot, but not like more than 1% of the population. Weird that we don't see any on the 2300AD map. Guess they're inaccessible, like how we assume that CT has more cities that we just don't see.