A large, relatively rigid segment of the Earth's lithosphere that moves in relation to other plates over the asthenosphere. (USGS)
James Daniell (compiler), Glossary of Earthquake Terms (shortened list of the most important terms), Earthquake-Report.com, Guam, USA 2011. http://earthquake-report.com/2011/02/15/glossary-o f-earthquake-terms-2/, (ND/ Erthq - Brit) {898}