( Earthquakes ( ( ( ( are ( caused ( by ( active faults ) ) ) ) ( , ( ( that is ) , ) ) ) ( faults ( along ( which ( ( ( the ( two sides ) ) ( of ( the fracture ) ) ) ( ( move ( with respect ) ) ( to ( each other ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Earthquakes)) (VP (VP (VBP are) (VP (VBN caused) (PP (IN by) (NP (JJ active) (NNS faults))))) (PRN (, ,) (INTJ (DT that) (VBZ is)) (, ,)) (NP (NP (NNS faults)) (PP (IN along) (SBAR (WHNP (WDT which)) (S (NP (NP (DT the) (CD two) (NNS sides)) (PP (IN of) (NP (DT the) (NN fracture)))) (VP (VBP move) (PP (IN with) (NP (NN respect))) (PP (TO to) (NP (DT each) (JJ other))))))))) (. .)))
Earthquakes are caused by active faults , that is, faults along which the two sides of the fracture move with respect to each other.
(ROOT (S (NP (DT A) (NN fault)) (VP (VBZ is) (NP (NP (DT the) (NN fracture)) (VP (VBN caused) (SBAR (WHADVP (WRB when)) (S (NP (NP (NNS rocks)) (PP (IN on) (NP (DT both) (NNS sides)))) (VP (VBP move))))))) (. .)))