20110729023949A

Prior to the turbulence event, the captain had the weather radar on and determined that it was safe for the flight attendants to get up and start their service. The seat belt sign was reported to be on at the time. Approximately 3 to 4 minutes after notifying the flight attendants it was safe to get up the flight encountered severe turbulence. According to the investigation, while in cruise flight climbing between FL230-250 approximately 75NM west of anrat navigation fix, the flight encountered severe turbulence for an estimated period of 30 seconds. There was one serious injury reported to a flight attendant who was thrown to the floor during the turbulence encounter. The injury was reported as a right knee and ankle. The flight attendant received a 2CM fracture to her right fibula requiring a sugar-tong splint. Facts:1. One female flight attendant received a 2CM fracture to her right fibula requiring a sugar-tong splint. 2. No reports of passenger injuries.3. There were no returns noted on the weather RADAR4. Flight crew reported entering rain showers at time of ENCOUNTER5. Initial weather analysis indicated turbulence was most likely result of convective activity 6. Initial FDR analysis shows peak vertical acceleration of positive .8G above the normal vertical acceleration.7. Since event occurred over the chinese mainland, the event was reported to caac who later delegated the investigation to the U.S. National transportation safety board.8. There was no aircraft damage.