At the time the Messiah will appear to the Nephites, that day will be accompanied with terrible destructions. There will be cities burned, there will be cities submerged, and there will be great quaking of the ground. These destructions will be accompanied by thunderings, and lightings, and earthquakes. All of these things will take place in the descriptions in 3 Nephi.
Here, there are prophecies. What is important is that Nephi declares that he has seen it. During his experience with the tree of life vision, he saw these future events, and described the thunderings and lightings, and the earthquakes that he saw in the vision. This connection to Nephi’s important vision is important because it will combine with the themes from Isaiah and become the foundation for Nephi’s exposition that will end 2 Nephi. Nephi is not only discussing Isaiah, but intermixing Isaiah to form a different version of the vision that he saw.
Nephi is declaring that his vision was true by using Isaiah’s prophecies to elucidate that vision.