Here the "snare" represents all the different bad things that will happen to people. People will run away to escape one bad thing but they will just experience another bad thing. (See: [[rc://en/ta/man/translate/figs-synecdoche]])
This speaks of large amounts of rain falling from the sky as if Yahweh opened a window in the sky and let the water pour through. Alternate translation: "The sky will split open and torrents of rain will fall" (See: [[rc://en/ta/man/translate/figs-metaphor]])
The word "foundation" normally refers to a stone structure that gives support to a building from underneath. Here it describes a similar structure that was thought to support and hold the earth in place. Isaiah says even the structure that holds the earth will shake. Alternate translation: "the earth will shake terribly" or "there will be a terrible earthquake"