A seismic wave that propagates through the interior of the Earth, as opposed to surface waves that propagate near the Earth's surface. P and S waves, which shake the ground in different ways, are examples
Christian Nerger and Johannes Schweitzer (Assisting Editor in Compiling), Glossary of Terms Frequently Used in Seismology and Observatory Practice, US Geological Survey (http://www.usgs.gov/), the Montana Bureau of Mines and Geology (http://www.mbmg.mtech.edu/) and the International Data Center of the CTBTO (http://www.ctbto.org), USA 2004. http://gfzpublic.gfz-potsdam.de/pubman/item/escido c:4141:2/component/escidoc:4142/Glossary_rev1.pdf% 3Bjsessionid=216960F299E7DC5292AAE080C9BACFB3, (ND/ Erthq - Amer) {25}