野島地震断層に伴う地表変位に関する新資料 -梨本地区の変位微地形および海岸・海域の地殻変動に関して- Some Additional Data on the Nojima Earthquake Fault of 1995, in Awaji Island, Southwestern Japan : Mapping of Detailed Fault Traces and Coseismic Coastal Deformation
This paper provides some additional data on the surface deformation associated with the Nojima earthquake fault, that occurred on January 17, 1995. These data were obtained mostly in March 1995, and include: 1) detailed mapping of the fault trace at the Nashimoto and Nojima sectors ; 2) coseismic coastal uplift on the northern part of Awaji Island; and 3) tide gauge data and displacement of supporting columns of the bridge between Awaji Island and Honshu, across the Seto Inland Sea. The main results are as follows.: 1) En eshelon fault traces and cracks are particulaly well developed at Nashimoto, underlain by unconsolidated alluvial sand and gravels. Small-scale reliefs, such as minor pullapart basins and minor pushed-up bulges, associated with the right-step or left-step of the rightlateral displacement of the Nojima earthquake fault, are clearly seen at Nashimoto 2) Coseismic coastal uplift is revealed by displacement of tetrapods (concrete blocks for wave brakes) at Ezaki (Loc. O) and by emerged beach deposits, about 300m east of Ezaki (Loc. P). This indicates that the southeastern side (upthrown side) of the earthquake fault was uplifted at the time of the 1995 earthquake. 3) Examination of releveling results of benchmarks, tide gauge data, and displacement of supporting columns of the bridge across the Seto Inland Sea, as well as the general pattern of active faults in the Kobe area, suggest that the northern extension of the Nojima fault has subsided and this probably represents a large scale pull-apart basin, due to right-step of major faults, dominated by right-lateral offset.
- 地理学評論. Ser. A
地理学評論. Ser. A 69(5), 353-364, 1996-05