Emirates Airlines flight EK764, an Airbus A380-861, operated a scheduled passenger flight, EK763, from Dubai International Airport (OMDB), the United Arab Emirates, to Johannesburg Tambo International Airport (FAOR), Republic of South Africa. The Aircraft had 526 persons onboard, consisting of two flight crewmembers, 24 cabin crewmembers and 500 passengers. The commander, occupying the left seat, was the pilot flying (PF). He stated that prior to the turbulence encounter, the daylight flight was uneventful with no avoidance actions required due to weather. After entering BEIRA flight information region (FIR), Mozambique, at flight level (FL) FL400 close to waypoint OKBIM, the flight crew stated that there was light turbulence with the weather radar displaying that the weather was off-path on the navigation display (ND) and beneath the aircraft. Soon after, several magenta spots appeared on the weather radar along the flight path indicating that there were areas of wet turbulence within 40 nautical miles (NM) ahead of the aircraft. At 1314:24 UTC, approximately six hours after departure from OMDB, the aircraft experienced moderate to severe turbulence at FL400 within BEIRA FIR. The operational flight plan (OFP) significant aeronautical weather chart had forecast the occasional presence of convective weather activity containing embedded cumulonimbus clouds (CB) up to an altitude of 52,000 feet (ft) in this area. During the turbulence encounter, the Aircraft autopilot and autothrust remained engaged and there were no operational exceedances. The turbulence lasted for approximately 30 seconds and resulted in a serious leg injury to an unsecured passenger on the upper deck. There was no reported damage to the aircraft cabin. The commander decided to continue the flight to the destination as the passenger?s injury was non-life threatening and the aircraft performance was not affected. The remainder of the flight, lasting 1 hour 46 minutes, was uneventful. Causes The Air Accident Investigation Sector of the United Arab Emirates (AAIS) determines that the cause of the Accident was the severe turbulence of vertical gust forces imposed on the Aircraft as it operated within an area associated with wet turbulence cells, resulting in the forceful movement of unsecured passengers and cabin crewmembers. Contributing Factors The Investigation determines that the following were contributory factors to the Accident: (a) After entering BEIRA FIR and wet turbulence was detected by the weather radar turbulence function, the flight crew did not use the full capabilities of the weather radar to obtain an accurate assessment of the distance of the area of greatest threat from the Aircraft flight path. (b) There was insufficient time for the cabin crew to secure the cabin after the seat belt sign was turned ON.