Aesthenosphere : The highly viscous mechanically weak region of the upper mantle of the Earth. It lies below the lithosphere, at depths between 100 and 200 km below the surface, but perhaps extending as deep as 400 km. (Wikipedia)
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}