Just wanted to share a few links to some stuff I've read lately regarding Total Electron Content and earthquakes.

[note that articles to arXive.org are often preprints and are likely not peer-reviewed]

Tōhoku quake coincided with sky 'anomalies' - physicsworld.com
http://physicsworld.com/cws/article/news/2011/may/26/tohoku-quake-coincided-with-sky-anomalies

Anomalous TEC variations associated with the powerful Tohoku earthquake of 11 March 2011 - Natural Hazards and Earth System Sciences (Open Access Journal of the European Geosciences Union)
http://www.nat-hazards-earth-syst-sci.net/12/1453/2012/nhess-12-1453-2012.html

Total electron content disturbances prior to Great Tohoku March 11, 2011 and October 23, 2011 Turkey Van earthquakes and their physical interpretation - arXive.org
http://arxiv.org/abs/1205.6118

Atmosphere-Ionosphere Response to the M9 Tohoku Earthquake Revealed by Joined Satellite and Ground Observations. Preliminary results - arXive.org
http://arxiv.org/abs/1105.2841

J.N. Thomas, USGS-EHP Final Report (G11AP20177) - Northwest Research Associates (www.nwra.com)
http://earthquake.usgs.gov/research/external/reports/G11AP20177.pdf

The resonant response of the ionosphere imaged after the 2011 off
the Pacific coast of Tohoku Earthquake - letter to Earth, Planets, Space
http://www.terrapub.co.jp/journals/EPS/abstract/6307/63070853.html

Brian