(S (S (BASENP (NNS Seismologists)) (VP (VBD said) (SBAR (S (BASENP (DT a) (JJ similar) (NN incident)) (VP (VBD happened) (PP (IN on) (NP (BASENP (DT the) (NN day)) (PP (IN of) (BASENP (DT the) (JJ original) (NNP August) (NN 6) (NN cave) (RP in)))))))))) (PERIOD .))