In case an earth quake hits Tokyo, it's a chance. The sentence is indeed poor English, to the extent that the meaning is completely obscured. Perhaps the speaker meant "The case of an earthquake hitting Tokyo is a chance." (not that it is natural English, but, if it does reflect the speaker's intent, it would have been intelligible.)
Possible interpretations for chance would vary depending upon the context, and could include meanings of risk, opportunity, or probability. (there isn't much chance that "opportunity" would be correct, but it remains possible.)
"In case an earthquake hits Tokyo" would ordinarily indicate that some sort of precaution is in place: (Food has been stockpiled in case ~ / In case ~, food has been stockpiled)
All that aside, "There is a chance that an earthquake will hit Tokyo" presents no difficulty (chance would take the meaning of risk or possibility.)
EDIT: Forgot to mention another use of chance: Usually as an adjective, or following an adjective: indicating a random event, or an event without apparent cause. Pure/blind/mere chance. Chance ~. (e.g. chance encounter, 出会える )
Last edited by 運転者 (2008-11-12 05:39:49)
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