Abstract
Liquefaction and fluidization are seen at many outcrops in the middle Pleistocene Kami-iwahashi Formation in the northern area of Chiba Prefecture, Japan. The lower part of Kami-iwahashi Formation consists of fluvial deposits (sands) and wetland deposits (muds) in ascending order. The sands show deformed cross-bedding with homogenizd texture. The muds show clastic dike and clastic sill. This field evidence shows that the sands were liquidized, and intruded into the muds. The district, where both deformed cross-bedding and intrusion are exposed, is surrounded by only deformed cross-bedding area. The trigger mechanism of the liquefaction and fluidization is interpreted as seismic shock because of the features, geographical pattern and limited horizon of the deformational structures.
