[SGL34-P04] Why and where submarine mud volcanoes existing? A case study of the Kumano Basin, Naikai Trough subduction zone
Keywords:mud volcano, plate convergent margin, mud intrusion/dirpir
MV on and around Japan Island is reported on land (Niigata and Hokkaido area, and hot mud pools) and also at submarine environments (off-Tanegashima and Kumano Basin). There are at least 14 of MVs in the Kumano Basin, the forearc basin at off Kii peninsula (Kuramoto et al., 1998, 2000; Morita et al., 2004; Pape et al., 2015, Asada et al., submitted). Kumano Basin is forearc basin overlying an older accretionary prism along the Nankai Trough, where Philippine Sea Plate subducts under the Eurasia Plate (Moore et al., 2009; Boston et al., 2016). A megasplay fault from the base of the accretionary prism cuts to the seafloor (Moore et al., 2009; Kimura et al., 2011). A fluid sampled from a MV in the Kumano Basin indicate that it comes from deeper than 15 km below seafloor, possibly meaning along plate boundary (Nishio et al., 2015). Results from seismic survey over the Kumano Basin partly show diapiric structure below MVs in the northern Kumano Basin (Morita et al., 2004; Moore et al., in this session). A recently confirmed MV along the Kumano Basin Edge Fault Zone (Asada et al., submitted; Walter et al., in this session) also is considered existing with larger mud diapir nearby, and maybe activated by faults cutting surface of the diapir (Asada et al., submitted). Trying overview the MVism in the Kumano Basin, to pick up characteristic feature of this area, a possible scenario is: (1) ejecta from MV maybe derived from accreted part, (2) environment below a lower sediment layer may decide presence of mud diapir and rough distribution of connecting MV, and (3) tectonic deformation near seafloor controls activity of each MV. Comparative discussion with other submarine MVs are efficient for further understanding of MV in the Kumano Basin. An original depth, history, degree of volcanism, differences between each MV, to know unknown MVs around Japan, and relationship with earthquake remains as unsolved problems.