Wikipedia says he lives in Chiba (which is where that gas plant was busily blowing itself up right after the quake).
His blog was last updated March 1, but he goes several days between posts from the look of things.
For what it's worth, Rei Hiroe (Black Lagoon's author) appears to be OK. There is a Twitter account that appears to be him, though it's not "verified" like other celebrity accounts are. It was last posted in 2 hours ago.