(1) Osaka City University, Osaka, Japan
Abstract: Neotectonics of the Quaternary Osaka Group; evidence from the southern part of Osaka plain, southwest Japan
In the study area the occurrence of active structures characterize the neotectonic distribution within and around the Osaka plain, along Osaka bay in Kinki district southwest Japan. Buried active structures consist of anticlines, faults and flexures within the basin lied beneath the ground under heavily populated areas, and the structures around the basin boundary consist of thrusts, normal faults and flexures along the mountainous area. The long-ranged Median Tectonic Line serves as the boundary for the southern part of the plain.
The Quaternary Osaka Group in the southern area consists of Sennan, Kokubu and Senpoku Formations, attains more than 390 m. in thickness and is composed of unconsolidated gravel, sand, silt and clay beds of limnic, fluvial and marine origin with more than 45 tuff beds.
This paper attempt to outline the field, placing it in regional framework and detailing some of the studies to elucidate the deformation process. The result shows that the neotectonics on the surface characterized by scarps, fault breccia, gouge and terrace deposit displacement mainly in NE-SW direction. Minor fault study generally exhibits axes of maximum compressive stress in ENE-WSW orientation, consistent with regional axis and correspond with the occurrence of Median Tectonic Line in southwest Japan.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana