I think Hollywood has tricked many of us when it comes to earthquakes.. If you aren't at the center, you basically get a bunch of rocking. A tank in decent condition can take some uneven pressure like that for short durations no problem. Now the issue is when a tank isn't level and is subjected to continued stress over the course of months and years. That's when you get failures.
A bunch of rocking? Shook me right off my bed when we had one hit here a good 10 years ago, and i was nowhere near the center. Also collapsed some stuff around the sound. When a quake hits it's like dropping a pebble in a lake, big ripple effect.
Edit: Forgot you all arent from this area. The sound = puget sound.