The verb in the sentence is resulted.
You can parse the sentence like this, where [X] is the subject of the sentence:
The [X] resulted in many safety reforms.
The [sinking of the ship after it collided with an iceberg] resulted in many safety reforms.
It's the same general construction as this:
The [fire] resulted in many safety reforms....
Neither are the predicate verb. "Sinking" is used as a noun (gerund)... it fou ere not sure, notice the article before it. "After it collided" is a dependent clause.
Look for another verb in that sentence.