(S (S (PP (VBG According) (PP (TO to) (NP (BASENP (DT the) (NNP United) (NNPS States) (NNP Geological) (NNP Survey)) (PRN (LRB -LRB-) (BASENP (NNP USGS)) (RRB -RRB-))))) (S (NP (NP (QP (ADVP (IN at) (JJS least)) (NN two)) (NNS earthquakes)) (PP (IN with) (BASENP (DT a) (NN magnitude) (NN 7.2) (CC and) (NN 5.1)))) (VP (VBP have) (VP (VBN rocked) (NP (BASENP (DT the) (NN island)) (PP (IN of) (BASENP (NNP Vanuatu)))))))) (PERIOD .))