Amos uses this question to remind people of what they already know about what happens when a trumpet sounds. This question can be translated as a statement. Alternate translation: "When the trumpet sounds in the city, the people will tremble." or "When the trumpet sounds in the city, we expect that people will tremble." (See: [[rc://en/ta/man/translate/figs-rquestion]])
The purpose of sounding the trumpet is to warn people that enemies are about to attack the city. Alternate translation: "If someone blows the trumpet in the city to warn the people about an enemy attack" or "If the warning trumpet is blown in the city" (See: [[rc://en/ta/man/translate/figs-explicit]])
The reason for trembling can be stated clearly. Alternate translation: "tremble because they are afraid" or "be afraid of the enemy and tremble" (See: [[rc://en/ta/man/translate/figs-explicit]])
Amos uses this question to remind the people of what they should already know about what causes a disaster. This question can be translated as a statement. Alternate translation: "If disaster overtakes a city, Yahweh has sent it." or "If disaster overtakes a city, we know that Yahweh has sent it." (See: [[rc://en/ta/man/translate/figs-rquestion]])