Also, the way to mitigate earthquakes and thermal expansion are (albeit vaguely) mentioned in the alpha document: the tube rests on pylons and the overall structure deforms slightly.
http://www.spacex.com/sites/spacex/files/hyperloop_alpha-201...
It makes almost no difference if the tube is 20 m long or 200 km long. If a small section of the tube can withhold the pressure a long section can as well. And thinking we can't make a low pressure environment in a tube that's a few meters of diameter is... weird.