Location of the Murono mud volcano, Niigata, Japan. (A) Location of the study area in the Tertiary sedimentary basin in Niigata Prefecture and in the back-arc of central Japan. The blue star indicates the epicenter of the Niigataken Chuetsu-oki earthquake. (B) Location of the Murono mud volcano and distribution of folds (after Takeuchi et al. 2000). Red and blue lines indicate the anticline and syncline structures, respectively.