' s ▁interior ▁and ▁se ism ology ▁▁ ▁Det erm ining ▁the ▁physics ▁of ▁Earth ' s ▁interior ▁was ▁enabled ▁by ▁the ▁development ▁of ▁the ▁first ▁se ism ograph s ▁in ▁the ▁ 1 8 8 0 s . ▁Based ▁on ▁the ▁behavior ▁of ▁the ▁waves ▁reflected ▁off ▁the ▁internal ▁layers ▁of ▁the ▁Earth , ▁several ▁theories ▁developed ▁as ▁to ▁what ▁would ▁cause ▁var ian ces ▁in ▁wave ▁speed ▁or ▁loss ▁of ▁certain ▁frequencies . ▁This ▁led ▁to ▁scient ists ▁like ▁In ge ▁Le h mann ▁discover ing ▁the ▁presence ▁of ▁the ▁Earth ' s ▁core ▁in ▁ 1 9 3 6 . ▁Ben o ▁G uten berg ▁and ▁Harold ▁Jeff re ys ▁worked ▁at ▁explaining ▁the ▁difference ▁in ▁Earth ' s ▁density ▁due ▁to ▁compression ▁and ▁the ▁she ar ▁velocity ▁of ▁waves . ▁Since ▁se ism ology ▁is ▁based ▁on ▁el astic ▁waves , ▁the ▁speed ▁of ▁waves ▁could ▁help ▁determine ▁density ▁and ▁therefore ▁the ▁behavior ▁of ▁the ▁layers ▁within ▁the ▁Earth . ▁ ▁N omen cl ature ▁for ▁the ▁behavior ▁of ▁se ism ic ▁waves ▁was ▁produced ▁based ▁on ▁these ▁find ings . ▁P - w aves ▁and ▁S - w aves ▁were ▁used ▁to ▁describe ▁two ▁types ▁of ▁el astic ▁body ▁waves ▁possible . ▁Love ▁waves ▁and ▁Ray le igh ▁waves ▁were ▁used ▁to ▁describe ▁two ▁types ▁of ▁surface ▁waves ▁possible . ▁ ▁Scient ists ▁who ▁have ▁contributed ▁to ▁adv ances ▁in ▁knowledge ▁about ▁the ▁Earth ' s ▁interior ▁and ▁se ism ology ▁include ▁Emil ▁Wie ch ert , ▁Ben