Preliminary Report on the Stress Distribution in Nishiyama Oil Field, Niigata Prefecture

There are two kinds of folds in Nishiyama oil field. One is box type and the other similar type fold. Principal stress distribution studied by conjugate faults analysis indicates that the lateral compressional stress, approximately NW-SE in direction is responsible for the formation of main structural features in this oil field. This NW-SE stress is believed to form the similar fold in southeasten side of the field (Nagamine anticline). On the other hand, in central area (Ushirodani anticline), the rocks were domed up by comparatively shallow formations. Although this conclusion is presented tentatively, it is well consistent to the result of Link's model experimentation.