Engineering Geologic Aspects of Seismic Soil Liquefaction, Niigata City, Japan

The 1964 M7.5 Niigata Earthquake remains one of the most significant natural laboratories for understanding seismic-induced soil liquefaction and its dependence on geological setting. Among global field case histories, Niigata stands out for the exceptional docu-mentation of liquefaction triggering, lateral spread displacements, and soil–structure interaction. This paper reexamines the event from an engineering–geologic perspective, emphasizing how Holocene coastal and fluvial depositional processes beneath the Echigo Plain controlled the spatial and stratigraphic distribution of liquefaction during the 1964 earthquake. The most severe ground deformations occurred in fluvially reworked sands derived from three major Holocene dune and barrier-island systems (CSD1,2,3) formed along the paleo-shoreline of the Sea of Japan. The largest of these, a mid-Holocene transgressive barrier complex deposited 50–60 m of beach and aeolian sand between 8 and 5 ka B.P., now lies buried 5–8 km inland beneath fine-grained alluvial deposits. Tectonic downwarping and deltaic progradation by the Shinano and Agano Rivers re-distributed these sands into loose, saturated fluvial facies beneath modern Niigata City. Quantitative geotechnical analyses demonstrate that liquefaction occurs within these reworked Holocene units rather than anthropogenic fills.