Most railways in central Toyko and Kanagawa will be open all hours today.

The following JR East sections will be closed for some hours.

Kawagoe Line west of Kawagoe and Hachiko Line.
Oume Line west of Kabe.
Sagami Line.
Narita Line Abiko-Narita.  (Trains to airport do not use this section)
Ryoumou Line.
Kururi Line.

Exact time frames of line closures available here:
http://www46.atwiki.jp/earthquakeinfo_en/pages/15.html