Tokyo Electric Power Company has subdivided the blackout zones, but 
there is not much visible change on railroad operations.

Several rail lines on the outskirts will closed for some hours.
They are all quite far from central Tokyo.  The Sagami Line reopened, 
but it too will be closed for some time today.

Other major operators say that no sections will be closed.

Details here:
http://www46.atwiki.jp/earthquakeinfo_en/pages/15.html