Learn French: Il est peu probable que le séisme détruise la ville. - It is unlikely that the earthquake will destroy the city.

The phrase il est probable que expresses a strong likelihood, so it takes the indicative. However, adding peu changes the meaning to 'it is unlikely.' Expressions of doubt or improbability—like il est peu probable que or il est improbable que—always trigger the subjunctive because the outcome is no longer seen as a sure thing.

The English translation says 'will destroy', so why aren't we using a future tense for the French verb?

French does not have a future subjunctive tense. When a phrase requires the subjunctive, like il est peu probable que, the present subjunctive (détruise) does double duty and covers both present and future actions.

How is the subjunctive form détruise constructed here?

For most verbs, including détruire, you find the subjunctive stem by taking the ils/elles form of the present indicative (ils détruisent) and dropping the -ent. That gives us the stem détruis-, to which we add the standard subjunctive ending for the third-person singular (-e).

Is there a difference between un séisme and un tremblement de terre?