In this task, we ask you to rewrite a sentence in simple English without changing its general meaning. Essentially, you want to make the sentence easier to read by using simpler words, utilizing more straightforward sentence structures, and omitting non-essential information etc.
Q: Scientists later looked back to the hours before the eruption and noticed that several long-period earthquakes , which start out strong and then slowly die out , had occurred in the final hours before the eruption .
A: 
Scientists later looked back to the hours before the eruption and noticed that several long period earthquakes had occurred .