I actually heard of a third slightly before I posted but although I found quite a few references to it, I couldn't find a good primary source. If it happened, it's near Zhenghou City.

Obviously the humanitarian side of things is pretty bad but it could be a mixed bag for Bitcoin and stocks. There is also talk that the three gorges dam might be under increased pressure and if that fails, it would affect China's major industrial area and could threaten 100 million people (I don't have much solid on this though).