Three-dimensional (3D) pre-stack depth migrated seismic data are used to analyse the geometry and growth of shallow faults associated with tectonic shortening in four (4) prominent thrust anticlines off Nankai, SE Japan. The four thrust anticlines show a trenchward increase in horizontal shortening and deform the seafloor at present. They shortened the overburden strata by 7143 m in the Late Quaternary, reflecting a horizontal shortening of 32.9% in response to plate subduction. A significant number of closely spaced and segmented fault arrays is observed in their hinge regions. Vertically segmented fault arrays with local throw maxima between 5 and 14 m relate to the existence of more competent (strong) intervals, or layers. Incompetent (weak) intervals record relatively small throw values between 2 and 5 m. We show that the presence of closely spaced, segmented fault arrays at shallow stratigraphic levels can have a significant impact on local stress distribution, controlling near-seafloor strain in accretionary prisms as Nankai's. The observed mechanical layering is likely to continue at depth to control the accumulation of tectonic stress in faults posed to reactivate during seismic events.

使用三维（3D）叠前深度偏移地震数据来分析日本东南部海域四（4）条突出逆冲背斜中与构造缩短相关的浅层断层的几何形状和增长。四个逆冲背斜线显示出水平缩短的增加，目前使海底变形。他们在第四纪晚期将上覆地层缩短了7143 m，反映了因板块俯冲而水平缩短了32.9％。在它们的铰链区域中观察到大量紧密间隔和分段的断层阵列。垂直分段断层阵列的局部投掷最大值在5和14 m之间，这与更有效的（强）间隔或层的存在有关。不称职（弱）间隔记录了2到5 m之间的相对较小的投掷值。我们表明，在浅层地层中紧密间隔的，分段的断层阵列的存在可以对局部应力分布产生重大影响，控制像南开这样的增生棱镜中的近海底应变。观察到的机械分层很可能会继续在深度上进行，以控制在地震事件中可能重新活化的断层中构造应力的积累。