Is it correct to say
Tsunami coupling in the code 'helps determine' human casualty
i.e., is use of multiple verbs consecutively correct?
Also, is it 'help determine' or 'helps determine'?
The two verbs reference different things: helps relates to 'Tsunami coupling' here, while determine relates to an abstract "one"; moreover, there's a to elided in the sentence as well. Read it as:
Tsunami coupling in the code helps (one) (to) determine human casuality.
The verbs there are not actually adjacent. Even if they were, that would hardly matter since they are unrelated.
The sentence is grammatically correct.
meta: If you still find the structure a little complicated, you may want to ask the question on ell.stackexchange.com