In the last two weeks I think Japan has suffered from three large earthquakes (they were at least notable). It's just that this last one had the biggest effect. China I think has been hit by two earthquakes and New Zealand one...
As for why the one in China didn't make the news, I think it did, but with all the stuff going on in the world right now (the middle east blowing up, Japan's ongoing disaster, etc.), a "minor" earthquake in China is probably not newsworthy, especially if there weren't many deaths.