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Japan Aims for Best Marine Surveys as it Builds Two New JCG Research Ships

China is brazenly conducting marine surveys in Japan's EEZ near the Okinawa Trough. Japan must counter China's assertions with better data.



marine surveys
"Heiyo" is the largest survey ship of the Japan Coast Guard. She was commissioned in 2020 and is equipped with the latest research equipment. (Provided by Japan Coast Guard)

China has been increasing unauthorized marine surveys inside Japan's exclusive economic zone (EEZ) around the Senkaku Islands (Ishigaki City, Okinawa Prefecture). 

In response, the Japan Coast Guard (JCG) is building two new large marine survey vessels for deployment in the region from 2024. They will be equipped with unmanned observation vehicles, according to a knowledgeable official on January 21.

China is unilaterally asserting the right to extend its continental shelf in the East China Sea. It seeks the right to develop marine resources in the area. Japan's policy is to counter China's assertions with data. Therefore, the JCG is collecting scientific data to support the legitimacy of Japan's maritime boundaries. Geological analysis will be conducted using the state-of-the-art large survey vessels as part of the research effort.

ASV will be among the equipment installed on the new large survey vessel, says the official. That is, an unmanned observation vessel that can automatically navigate dangerous areas such as undersea volcanic zones. Accordingly, it will be equipped with instruments to measure water temperature, ocean currents, salinity, and other elements. In addition, the vessels will carry the latest research equipment, including an autonomous unmanned underwater vehicle (AUV) capable of diving close to the seabed.

marine surveys
Chinese oceanographic research vessel is conducting an unauthorized survey inside Japan's EEZ around Okinotorishima. Observation equipment, appearing to be a remotely operated vehicle (ROV), can be also confirmed at the stern. (July 2020, by Japan’s 3rd Regional Coast Guard Headquarters)

China's Unauthorized Surveys

According to the Japan Coast Guard, Chinese maritime research vessels have repeatedly conducted unauthorized surveys in the vicinity of the Senkaku Islands in the East China Sea, around the Okinawa Trough, and off Okinotorishima Island (Ogasawara Village, Tokyo), the southernmost point of Japan.

In EEZs and continental shelves, coastal states have the right to develop oil, natural gas, and other resources on the seabed. In the East China Sea, China and South Korea claimed in 2012 that their continental shelf extends to the vicinity of Japan's territorial waters east of the Okinawa Trough. Both claims cross the geographical median line with Japan.

Collecting and analyzing more precise seafloor topographic data is important in order to firmly refute the claims of China and others. To that end, the Japan Coast Guard has determined that it is necessary to maintain a large survey vessel equipped with the most advanced survey equipment.

Vital To Securing Japan's Maritime Interests

"Building a new, state-of-the-art survey vessel is meaningful. It allows us to accurately grasp the topography and fluctuations of the seabed," emphasizes Professor Yoshihiko Yamada. He is an expert on maritime policy and security at Tokai University.

The EEZ and continental shelf are defined by the United Nations Convention on the Law of the Sea. Coastal states are allowed to establish EEZs in the sea area up to 400 nautical miles (about 370 km) from the baseline of their territorial waters, the seafloor, and under the seafloor. 

This area of seafloor and subseafloor is called the continental shelf. The continental shelf can be extended if geological and topographical requirements are met. However, if the distance between two countries is less than 400 nautical miles, the boundary must be determined by agreement with the other country.

In the East China Sea, the shortest distance between Japan and China is less than 400 nautical miles. Therefore, Japan has established an EEZ east of the median line, in accordance with domestic law. In 2012, China and South Korea nevertheless unilaterally claimed that the area east of the Okinawa Trough is their continental shelf. Both claims cross the geographical median line between the respective countries and Japan. 

marine surveys
Chinese military vessels also hover near Okinotorishima Island.

Squeezing Japan

Chinese and South Korean claims extend up to the vicinity of Japan's territorial waters. Furthermore, they have each applied to the UN Commission on the Limits of the Continental Shelf, established under the UN Convention on the Law of the Sea, for an extension of the continental shelf.

According to the Japan Coast Guard, Japan's position is that the continental crust of the East China Sea is continuous and there is no room to extend the continental shelf. China and South Korea, however, claim that the continental crust breaks near the Okinawa Trough. 

A hearing of the Commission requires the consent of the countries concerned. In this case Japan has not agreed. Instead, it has asked the Commission not to review the applications of China and South Korea.

Deposits of rare earth metals and other minerals may possibly be present in the vicinity of the Okinawa Trough. If China's application for an extension is approved, it would create the right to develop the seafloor resources. 


Meanwhile, extension of the continental shelf south of Japan's southernmost Okinotorishima Island (Ogasawara Village, Tokyo) remains an issue. Japan has applied to international organizations for recognition. However, China has busily published a series of scientific papers between 2021 and 2022 that deny any geographical connection. In the background, it is believed China is aiming to prevent Japan from extending its continental shelf.

This Chinese Navy frigate sailed in Japan's continental zone around the Senkaku Islands in July 2022. (Provided by the Ministry of Defense.)

The Chinese Navy

However, there is another possibility in Professor Yamada's view. Given the situation in which the Chinese Navy is actively advancing into the Pacific Ocean, "It is possible that they are using the data on sea water temperature, water quality, and currents obtained from the survey of the seafloor topography for submarine navigation."

Meanwhile, if China's and South Korea's claims are recognized internationally, Japan will lose jurisdiction over its seafloor resources. In order to secure its maritime interests, Japan needs more precise geological data to disprove such claims.

Jun Tsuruta is an associate professor of international law at Meiji Gakuin University and an expert on coast guard administration. He pointed out that: "oceanic surveys should be encouraged to advance scientific knowledge. But consent must be obtained from the coastal state when conducting them in the [other state's] EEZ." 

He also emphasized that "it is important not to allow China to freely conduct surveys in Japan's EEZ, and marine surveys in Japan's EEZ should be regulated by law."


(Read the report in Japanese.)

Author: The Sankei Shimbun

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