10:45 AM - 12:15 PM
[MIS19-P02] Mud volcano field in Hyuga-nada, eastern offshore of Kyusyu Island, Japan
Keywords:Mud Volcano, Hyuga-nada, Seismic reflection survey, Acoustic mapping, Gas field
Mud volcanoes bring sediments and fluids from a depth of less than a dozen kilometers below the Earth's surface. For sediments to rise through the subsurface, they should either have sufficient buoyancy. Mud volcanoes over the world emit gas in many cases, which is important improcation for buoyancy acquisition. Traditionally, mud volcanoes are a geological feature that have been used for oil and natural gas exploration.
Such mud volcanoes in Japan are more common along the offshore areas than on the land. Currently, there are at least 14 mud volcanoes in the Kumano forearc basin of central Japan, a methane hydrate-bearing area.
The existence of mud volcanoes off the eastern coast of Kyushu Island was first discovered by an offshore industrial company in the 2000s. However, the area was not thoroughly investigated in focusing MV distribution from a scientific perspective. An acoustic investigation was conducted to identify the existence of several mud volcanoes from the Kumano Basin to the Hyuga-nada along the southwestern coast of Japan. The other investigation, 3D seismic surveys by domestic oil and natural gas explorations off the Miyazaki coast (2009–2013) provides high-resolution sub-seafloor geological structures over the area. Based on these shallow subseafloor structures, we identified another 27 mud volcanoes in the Hyuga-nada. We expect there several such volcanoes just outside the surveyed areas.
Based on acoustic surveys and sediment sampling, Ujiie (2000) found mud volcanoes or relative geological features ("Mud diapir and serge") from the off-Tanegashima to the offshore Amami Oshima. Moreover, Itaki et al. (2015; 2017) and Sato and Itaki (2015) have identified at least one mud volcano and 11 similar features offshore Kikaijima Island. The existence of a series of mud volcanoes from Hyuga-nada to the offshore Kikaijima Island would potentially suggest a huge mud volcano field, which wider and partially denser than the other known fields in the Kumano Basin. A geological explanation is needed to understand this uneven distribution of mud volcanoes. Subducted seamounts have been reported beneath the Kumano Basin. The subducting Kyushu-Palau Ridge and seamounts below the Hyuga-nada to the further southwestern area may be the key to solving submarine environments. The very low-frequency seismic events observed over the Kumano and Hyuga-nada areas may also be expected to relate the mud volcano distributions. This study used part of the data from domestic oil and natural gas survey off Miyazaki areas, led by the Ministry of Economy, Trade and Industry (METI).
Such mud volcanoes in Japan are more common along the offshore areas than on the land. Currently, there are at least 14 mud volcanoes in the Kumano forearc basin of central Japan, a methane hydrate-bearing area.
The existence of mud volcanoes off the eastern coast of Kyushu Island was first discovered by an offshore industrial company in the 2000s. However, the area was not thoroughly investigated in focusing MV distribution from a scientific perspective. An acoustic investigation was conducted to identify the existence of several mud volcanoes from the Kumano Basin to the Hyuga-nada along the southwestern coast of Japan. The other investigation, 3D seismic surveys by domestic oil and natural gas explorations off the Miyazaki coast (2009–2013) provides high-resolution sub-seafloor geological structures over the area. Based on these shallow subseafloor structures, we identified another 27 mud volcanoes in the Hyuga-nada. We expect there several such volcanoes just outside the surveyed areas.
Based on acoustic surveys and sediment sampling, Ujiie (2000) found mud volcanoes or relative geological features ("Mud diapir and serge") from the off-Tanegashima to the offshore Amami Oshima. Moreover, Itaki et al. (2015; 2017) and Sato and Itaki (2015) have identified at least one mud volcano and 11 similar features offshore Kikaijima Island. The existence of a series of mud volcanoes from Hyuga-nada to the offshore Kikaijima Island would potentially suggest a huge mud volcano field, which wider and partially denser than the other known fields in the Kumano Basin. A geological explanation is needed to understand this uneven distribution of mud volcanoes. Subducted seamounts have been reported beneath the Kumano Basin. The subducting Kyushu-Palau Ridge and seamounts below the Hyuga-nada to the further southwestern area may be the key to solving submarine environments. The very low-frequency seismic events observed over the Kumano and Hyuga-nada areas may also be expected to relate the mud volcano distributions. This study used part of the data from domestic oil and natural gas survey off Miyazaki areas, led by the Ministry of Economy, Trade and Industry (METI).