We investigated a mud volcano (MV) in a fault zone located at the southern edge of the Kumano Basin, the largest forearc basin along the Nankai Trough. Existing seismic sections show a truncated bottom-simulating reflection by a conduit below a topographic high, indicating the presence of an MV. New shipboard acoustic observations show that the fluid may be seeping through the seafloor, which in turn indicates that there are sufficient fluids for larger scale fluid migration in this area. Autonomous underwater vehicle-based high resolution acoustic observations and pH measurements indicate that soft sediment covers most of the MV and surrounding seafloor and that mud and small amounts of “high-backscattered materials” are sprinkled within the crater and around the MV. The MV type is different from those in the landward part of the Kumano Basin: the southern MV is smaller in size, has a steeper slope angle than the those in the northern Kumano Basin, and is located in a fault zone. The characteristics of this 14th Kumano Basin MV suggest that it is an expression of the larger scale fluid and sediment migration along the southern edge of the Kumano Basin, which may provide information regarding fluid and sediment migration along fault systems in the Nankai Trough accretionary prism.

我们调查了位于熊野盆地南部边缘的断层带中的泥火山（MV），这是南开海槽中最大的前臂盆地。现有的地震剖面显示了地形高处下方的导管截断的底部模拟反射，表明存在中压。新的船上声学观测结果表明，流体可能正在渗入海底，这又表明该区域有足够的流体用于大规模的流体迁移。基于自主水下航行器的高分辨率声学观测和pH值测量表明，软沉积物覆盖了大部分MV和周围的海底，并且在火山口内和MV周围撒有泥浆和少量的“高向后散射物质”。MV类型不同于熊野盆地陆上部分的MV类型：南部的MV较小，倾斜角度比熊野盆地北部的倾斜角度大，并且位于断层带。该第14个Kumano盆地MV的特征表明，它是沿Kumano盆地南边缘较大规模的流体和沉积物迁移的一种表现形式，这可能提供有关在Nankai Trough增生棱镜中沿断层系统的流体和沉积物迁移的信息。