The Continental Shelf Extension claims in East Asia

By now all countries have submitted their claim on UNCLOS, which states

• The continental shelf is defined as the natural prolongation of the land territory to the continental margin’s outer edge, or 200 nautical miles from the coastal state’s baseline, whichever is greater. State’s continental shelf may exceed 200 nautical miles until the natural prolongation ends. However, it may never exceed 350 nautical miles from the baseline; or it may never exceed 100 nautical miles beyond the 2,500 meter isobath (the line connecting the depth of 2,500 meters). Coastal states have the right to harvest mineral and non-living material in the subsoil of its continental shelf, to the exclusion of others. Coastal states also have exclusive control over living resources "attached" to the continental shelf, but not to creatures living in the water column beyond the exclusive economic zone.

The claims can be found here and here.

• Japan has submitted a 78-page long "executive summary", to which China and Korea challenged the legitimacy of Okinotori Rock, which USA (North Mariana Island, i.e. Saipan and Guam) and Palau reserved their rights on overlapping claims
• Korea and China each submitted their claims, both pushing the continental shelf to the Okinawa Trough
  
• (Note all 3 countries ratified UNCLOS, which DPRK did not)
  

Japan's continental extension claim focuses on the souther part of its EEZ claim (i.e. lower half of this map)

Consisting of 5 major areas:

• SKB Shikoku Basin, the large vertical strip south of Shikoku Island and north of the Okinotori 200 nm circle.
• The area between Ogasawara/Iwo Jima (OGP) and the Minami-tori Shima (island) 200 nm circle (MTS)
  
• KPR, the area between the Okinotori circle and Palau's 200 nm EEZ boundary (potential overlap)
• 2 smaller pieces ODR and MIT to the east and west of the Okinotori circle
  

A very nice map for Chinese and Korean claims can be found in the red firefly blog (a very nice map blog in Chinese)

• The orange area is the co-development zone (1st phase) reached by China and Japan a year ago
• The green area is the Joint Korea-Japan Fishing Zone
• Blues lines are the 200 nm lines for Korea and China
  
• KOR1-KOR5 are sample points (joined into a line) of Korean claim
• D1-D4 are sample points of Chinese claim
• Both the KOR and D points are where the continental shelf end at the Okinawa Trough
  

Here is the technical definition of China's calim

• A -- the base-point (land territory) where the claim distance starts to count (usually an island close to the continent)
  
• B -- 200 nm line
  
• C -- continental shelf slope start to fall (FOS), point of maximum change in gradient
  
• D -- deepest point when continent shelf falls to the trough (lowest sea level)
  

Note that China's "preliminary example point" has carefully avoided to overlap with Korea claim points, apparently for a few reason (that I can think of)

1. To avoid controversy with Korea
2. To have Korea on its side over a potential rebuff from Japan (Japan's argument may be quite weak given the fact that it also submitted similar claim to the other side of its ocean)
3. The example points are only "examples" to establish the Okinawa trough as the boudary, China can then negotiate with Korea (if the trough is established) regarding how to divide the trough between them, most likely it would be the equidistant principle which is not far from D1/KOR1

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Related:

• The East China Sea deal - details
• The funny shape of the East China Sea "co-development" zone
• Japanese Air-Defence Identification Zone (Map)
• Greedy Asians?
• Tsugaru Strait: Japanese territorial claim is not always "greedy"