When you said that you've got earthquakes.. that is what makes me think it's the building.

Buildings naturally move and shift throughout the year. In the summer, when things are really hot, they swell. In the colder seasons, they shrink. This causes natural fluctuations in the walls and the buildings. If you also have earthquakes then that adds another layer of complication.

The crack is small enough, and simple enough, that you could patch it yourself. If you have a hardware store, you can get a little bit of spackle with a brush and take care of it. Scrape the junk paint around it off, put a bit of water and spackle powder in a bowl, mix and then put it on the wall to let it dry. Then repaint!