Jonah to  Amos

Judgment determined.

Mercy

FE 10God saw their works, that they turned from their evil ways, and turned his fierce anger away from them and did not destroy them. A Proverbs 12:7 Jonah 3:10 (Jonah 3:10 BRB)
3Thus says the Master: For 3 transgressions of Damascus and for 4 I will not turn away its punishment, because they have threshed Gilead with threshing instruments of iron, Amos 1:3-5 (Amos 1:3 BRB)

Jonah goes to Nineveh, they listen to him, repent and God does not overthrow the city as he had threatened. In contrast, Amos opens with a message for a number of places where God says he will not turn away from punishing (as he did with Nineveh).

God turned his anger away from Nineveh, but Damascus and the other places in the list at the beginning of Amos are told that God will not "turn away their punishment." Why would Amos have this odd phraseology? Do people think God won't follow through? If they've just read Jonah, the preceeding book, they might think so. After all, God did stand down when the people of Nineveh repented. Given the way he softened towards Nineveh, in fairness, he is forced to say, explicitly, that the results will not be the same this time.

Call

FE 1The word of the Master came to Jonah the son of Matai saying, 2Arise, go to Nineveh, that great city, and preach against it; for their wickedness has come up before me. Jonah 1:1-23But Jonah rose to flee to Tarshish, from the presence of the Master, and went down to Joppa; and he found a boat going to Tarshish; so he paid the fare and went into it to go with them to Tarshish to flee from the presence of the Master. Jonah 1:3 (Jonah 1:1-3 BRB)
14Amos answered and said to Amaziah, I am not a prophet nor the son of a prophet. I am a shepherd and a gatherer of wild figs. 15The Master led me as I followed the flock and the Master said to me, Go prophesy over my people Israel. Amos 7:14-16 (Amos 7:14-15 BRB)

When Jonah heard the call to go warn Nineveh he fled in the opposit direction. Amos, however, just went when called.

Jesus says a prophet is without honor in their home town. Jonah, fortunately, wasn't called to his home town, but to Nineveh, essentially a group of strangers. Amos on the other hand is called to go warn his neighbors, Israel. Nineveh hears Jonah, the stranger, but Israel does not hear Amos. Despite having the harder assignment due to the "home town" principle, Amos goes.

Secrets

FE 1But it displeased Jonah exceedingly, and he was greatly grieved. 2He prayed to the Master and said, I ask, Master, was this not what I said when I was yet in my country? That is why I fled before to Tarshish for I knew that you are a favorful and merciful god, patient and of great kindness, and you are ready to turn away calamity. E Exodus 34:6 Jonah 4:1-3 (Jonah 4:1-2 BRB)
7Surely the Master of masters does nothing without revealing his secret to his servants the prophets. Amos 3:78The lion has roared who will not fear? The Master of masters has spoken who can but prophesy? Amos 3:8 (Amos 3:7-8 BRB)

Jonah had a reason to run, though. He knew that God would relent in the end and he would look like a false prophet. Imagine, go deliver this message so they will repent and I don't have to destroy them. God gets what he wants, the people are not destroyed and have a better quality of life for their repentance and Jonah, well, he looks false to those who don't understand what happened. No wonder he goes off and sits alone on a distant hill.

Jonah knew God was going to show compassion, so he didn't want to go. He was more concerned with his appearance or what they might to do him if they thought he was a false prophet then saving Nineveh from destruction. Amos says God does nothing without first revealing his secrets to his servants the prophets. Jonah was savvy to what God was doing, he knew the secret that God's threat to destroy Nineveh was designed to bring repentance and would not happen. He runs to Tarshish to avoid the whole thing, but God causes storms and whales and humbling circumstances to bring Jonah back to the original call. As Amos says, Master has spoken, who can but prophesy. Even fleeing to Tarshish doesn't stop the reluctant prophet from delivering God's message.