Bobcat:
Secular dating puts Jonah's visit to Ninevah possibly on the heals of these events adding reason to why the Ninevites reacted possitively to Jonah's message.
I would not like to speculate about 'Jonah', as that story smacks of folklore. Amos' 'prophecy', like many biblical and extra-biblical ancient writings, was more likely a historical account presented as 'prophecy' as a narrative device. (The fact that it includes the statement, 'two years before the earthquake' is a pretty big clue that it was actually written afterwards but retrodated.) However, it at least includes specific points of reference. The story about 'Jonah' provides nothing usable at all, because the net result is that nothing happened.