報告書番号

U98048

タイトル（和文）

基盤の断層変位に伴う第四紀層及び地表の変形状況の検討（その2）-正断層，逆断層模型実験-

タイトル（英文）

Deformation of Quaternary Deposits and Ground Surface Caused by Bedrock Fault Movements (Part 2) -Normal and Reverse Fault Model Tests-

概要 （図表や脚注は「報告書全文」に掲載しております）

基盤の正断層，逆断層変位に伴い第四紀層等の未固結被覆層及び地表がどのように変形するのかを解明するため，断層模型実験による検討を行った．剪断層は雁行状に配列しながら発達し，底盤の断層が正断層の場合には，そのほぼ直上の地盤表面に到達するが，逆断層の場合の剪断層の地表到達位置は，底盤の断層傾斜角により大きく異なる．剪断層の地盤表面到達位置／地盤の層厚(W/H)は、Hにより大きく変化せず，地震断層におけるW/Hと良く一致する．剪断層が地盤表面に到達するのに必要な底盤の断層変位量/地盤の層厚(D/H)は，底盤の断層が逆断層の場合，2～10％，正断層の場合，1～3％程度で，特に低角逆断層の場合，大きな値を示す。本実験で得られたD/Hの値は，地震断層におけるD/Hとほぼ一致する．

概要 （英文）

The deformation form of the Quaternary deposits caused by dip-slip on the bedrock faults is studied by means of the model experiments.The fault model tests simulating normal and reverse faults by changing the parameter of the fault type, the fault dip, the fault displacement, the thickness of the overburden (sand mass) and the grain size of the sand reveal the following. The development pattern of shear bands strongly depends on the fault type and the fault dip of the basement. The shear bands are not shown as one linear plane but as en echelon pattern. The en echelon pattern depends on the grain size of sand and the thickness of the sand mass.  The location of the surface fault rupture strongly depends on the fault type, the fault dip and the thickness of the sand mass. In the case of the normal fault, the location of the surface fault rupture is just above the bedrock faults, which have no relationship with the fault dip. On the other hand, the location of the surface rupture of the reverse fault has closely relationship with the fault dip. The horizontal distance of surface rupture from the bedrock fault normalized by the height of sand mass (W/H) does not depend on the height of sand mass. The values of W/H from the test agree well with those of earthquake faults.  When the fault rupture develops at the surface through the overburden, the fault displacement of the reverse fault in the bedrock is larger than that of the normal fault.The normalized base displacement required to propagate the shear rupture zone to the ground surface (D/H) from the test agrees well with those of earthquake faults.

報告者

キーワード