My slinky-style seismograph measures vertical displacement best. And when this 30 second long quake struck, the seismograph was left shaking for over 14 minutes. Over 20 aftershocks were detected over the next 21 hours. Aftershocks are still being detected 24 hours later.
The time between the arrival of the P and S wave is on the order of 15 seconds. The P wave arrives first because it travels the fastest. The S wave is slower and if we measure the difference in their arrival times, we can determine the distance to the earthquake's epicenter. Grom what I see on earthquake tables, a difference of 15 seconds is about 150 km, or 91 miles.
Seismogram of the earthquake and many of its aftershocks
|The extracted earthquake and first aftershock|