Please choose the correct answer to the question: Two seismographs are placed 500 km from an active fault line, one on each side of the active fault line. During an earthquake, what most likely accounts for the different readings on the seismographs?

Answer1: the pull of gravity on the waves Answer2: the interaction of light with waves Answer3: the differences in the strength of the waves' origins Answer4: the different media through which the waves travel

Answer format: answer1/answer2/answer3/answer4
Answer: answer4