Provide your best answer for the following question. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The question is: 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?
the different media through which the waves travel
Distance from the epicenter, different sides of the fault.