Japan Institute for National Fundamentals

　　　　　On July 22, the Japanese government unveiled photos of Chinese offshore platforms under construction in the East China Sea. As the international energy market now sees oversupply, China has imported massive natural gas from Turkmenistan, Kazakhstan and other countries since 2010. Therefore, China has no high priority to construct more than two digits oilrigs in the East China Sea at this time to secure more energy supply.

China could deploy sensor and weapon systems on platforms
　　　　　In November 2013, China set up an Air Defense Identification Zone (ADIZ) covering Japan's Senkaku Islands and part of Japan's exclusive economic zone in the East China Sea. But radar sites at the continental China alone cannot monitor the entire ADIZ. By installing surveillance and reconnaissance systems on the unveiled offshore platforms, China could put the almost entire ADIZ under its surveillance.
　　　　　Such systems include radars, Electronic Support Measures (ESM) for detecting radio waves, Signals intelligence devices, and helicopters as well as UAVs for surveillance and reconnaissance flights. They may also include sonar devices for underwater surveillance, which may fail to effectively be used under the relatively shallow East China Sea.
　　　　　Sensor systems are roughly divided into two categories -- active sensors for emitting electronic as well as sound waves and passive sensors only for detecting electronic as well as sound waves emitted by targets. Passive sensors are more unfavorable than active sensors for targets because they cannot know whether they are detected or not. A passive sensor can find directions of targets but not distances. But multiple passive sensors can be integrated to find out target fixes.
　　　　　Weapon systems could be deployed on offshore platforms for attacking targets. While ballistic missiles to be launched into outer space may not be available on fragile offshore platforms, cruise missiles and anti-air weapons may be deployed on these facilities.
　　　　　Those sensor and weapon systems can enhance the effectiveness of China's warning to use force for taking defensive emergency measures if foreign aircraft entering her ADIZ refuse to comply with Chinese instructions.

China could siphon off Japanese natural gas
　　　　　China has conducted slant-drilling technic up to 8 kilometers at her Xi River oilrig off Hong Kong. As gas fields named by Japanese as Shirakaba and Kashi and the third platform among the unveiled Chinese facilities are located within 5 kilometers from the Japan-proposed median line between Japanese and Chinese exclusive economic zones, China could siphon off natural gas from the Japanese side of the line. Some reports say the Shirakaba and Kashi gas fields stride across the median line so that China could use even vertical-digging to siphon off gas from the Japanese side.
　　　　　China is attempting to transform the South China Sea, where it is reclaiming around reefs, and the East China Sea, where it is constructing offshore platforms, into her inland sea. The attempt may be natural given that China enacted her territorial water law in 1992 to exert its sovereignty over the almost whole of the East and South China Seas and that the People's Liberation Army's inside defense policy sought to secure sea control within the so-called first island chain (linking Japan, Taiwan, the Philippines and Borneo Island) by 2010.

Fumio Ota is a JINF Planning Committee Member and retired Vice Admiral of Japan’s Maritime Self-Defense Force.