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Earth's seismic ve;oc ty increases with depth

FIGURĘ 5.7 Seismic waves tnu-el n: ditfferent yelocities through iliffo.ronr marena Is These \vaves rctract, or bend, upon encnnnrering tl’r bojndary between iwo diffcrent maieriah. They ;.il«o her.d if velociry earies concinuousLy. (a) A refracled ruy i.ruveling chrough ii :«gior n which ihe v.elocity d cudi lay.er i' higher than rhc one abovc t. (b) If Earth had eenstaru yclucily, scisimc rays -wouU ^ '■•raight iines. (e) Tac veloeity ot a seismic wave actually increases wich incrcasing dopili m Eanli. A.s a resuLt, die seismic w.iyes laerul) śfccept for a ray iluu traveU yertically dcwnwnrd, which passes righr through undcilocicd.