On August 5, 2012, about 0912 eastern daylight time, Republic Airlines, Inc.,(doing business as US Airways Express), flight 3133, an Embraer S.A. ERJ 170-200 LR, N134HQ, encountered turbulence while over the Atlantic Ocean near Hilton Head, South Carolina, during an en-route descent. There were no injuries to the airline transport rated captain or first officer, 2 flight attendants, or 71 passengers, while one passenger sustained serious injuries. The airplane which was not damaged was being operated under the provisions of 14 Code of Federal Regulations (CFR) Part 121 as a scheduled domestic passenger flight from Philadelphia International Airport (PHL), Philadelphia, Pennsylvania, to Jacksonville International Airport (JAX), Jacksonville, Florida. Instrument meteorological conditions prevailed at the altitude, and location of the turbulence, for the flight, which operated on an instrument flight rules (IFR) flight plan. According to a chronological summary of communications, the flight was cleared to takeoff at 0755, and proceeded towards the destination airport, during which, air traffic control (ATC) communications were transferred to several different facilities. The captain stated that when the flight was near Charleston, South Carolina (while in contact with the Jacksonville Air Route Traffic Control Center (Jacksonville ARTCC)), they began descent from the cruise altitude. Knowing the weather was deteriorating ahead, he decided to turn on the seatbelt sign early for safety reasons. The “B” flight attendant who was in the back galley of the airplane later reported that after the seatbelt sign was turned on, he made, “…the seat belt announcement.” The captain further reported that during the descent, the flight encountered what he described as a small pocket of light to moderate turbulence which lasted approximately 2 to 3 seconds, then smoothed out for most of the remainder of the flight, with some chop reported. About 1 minute after encountering the turbulence, one of the flight attendants contacted the flight deck and reported injury to one passenger who had gotten up after the seatbelt sign was illuminated and the seatbelt announcement was made. The captain made an announcement about the need to remain seated with seatbelts fastened, and called to the destination airport operations and requested medical equipment be standing by. According to the transcription of communications with Jacksonville ARTCC, there was no record that the pilot advised air traffic control of the turbulence encounter. The flight continued to the destination airport and landed without incident, where the injured passenger was transported to a local hospital for treatment of her injuries. A relative of the passenger who sustained the serious injury and who was travelling with her reported that a connecting flight prior to the accident flight was delayed, and after landing they were rushed to board the airplane for the accident flight. Before the turbulence encounter he reported hearing an announcement to fasten their seatbelts; however, the passenger believed this was because the flight was close to the destination airport, and not related to weather conditions. As such, the passenger who was injured left her seat and walked to the lavatory, where, while out of her seat, the flight encountered “…heavy turbulence which threw her to the floor”, resulting in her injuries. The relative of the injured passenger and a flight attendant moved her to another seat where she remained for landing.