( There ( ( ( are also ) ( ( two types ) ( of ( ( ( surface waves ) , ) ( which ( tend ( to ( arrive last ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (EX There)) (VP (VBP are) (ADVP (RB also)) (NP (NP (CD two) (NNS types)) (PP (IN of) (NP (NP (NN surface) (NNS waves)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBP tend) (S (VP (TO to) (VP (VB arrive) (ADVP (RB last)))))))))))) (. .)))
There are also two types of surface waves, which tend to arrive last.
(ROOT (S (NP (EX There)) (VP (VBP are) (NP (NP (CD two) (NNS types)) (PP (IN of) (NP (NN surface) (NNS waves))))) (. .)))