Well, we don't know if it's the CLOSEST one, but it's closer than the other ones on this print-out.
There are actually three clues to this in the seismograms:
1). The waves from the tremor reach the Wink station first ... the P wave gets there 50 seconds before Chicago and 3 whole minutes before Tampa.
2). They are stronger (greater amplitude) at Wink than at Chicago or Tampa.
3). The delay between the P wave and the S wave is the smallest at Wink. This delay between the two waves grows as the detector is farther from the quake.
