Hacker News Reader

I live about 9km away from the site of the blast(as the crow flies). I can definitely confirm that the order of events was:

1 - Earthquake

2 - Sound (sounded like rolling thunder or a jet breaking the sound barrier)

3 - Pressure wave (felt as a sudden, short-lived, strong wind at that distance)

View on HN

I am curious about 2 and 3. Since sounds is also just a pressure wave, those two should have been the same speed as well. I guess the sounds must have travelled through the ground as well.

The speed of sound in pretty much any solid (or liquid) body is much faster than in the air. That's why the earthquake came first, and it was probably the earthquake that caused the 2. noises.

This is explained in the article. It describes the pressure wave as moving slower than the speed of sound. It was not a shockwave which would be generated by high-explosives which would travel at the speed of sound and be much more deadly.

Reply on news.ycombinator.com