On September 15, 2014, about 1230 Pacific daylight time, a Piper PA-28-150, N5948W, experienced severe vibrations and the pilot initiated a forced landing onto a meadow about 15 miles southwest of Lone Pine, California. The pilot was seriously injured, and the airplane sustained substantial damage to both wings. The airplane was registered to and operated by the pilot as a personal flight under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and no flight plan was filed for the flight which departed from Reid-Hillview Airport of Santa Clara County, San Jose, California at 1040. The pilot reported that two hours into the flight he observed a "flash of something" depart the front of the airplane; the airplane instantly began shuddering and vibrating violently. The pilot immediately reduced the throttle to idle and found a clear spot to land. With the engine at idle the pilot could see that about half of one of the propeller blades was missing. He also observed considerable movement of the front of the airplane. He descended the airplane rapidly to the clearing; as he approached the clearing, he observed large rocks that the airplane barely cleared. He held the nose of the airplane up as long as possible; the left landing gear touched the ground first and separated from the airplane followed by the right landing gear. As the nose wheel touched down it also collapsed and the airplane slid on its belly until it impacted a rock and came to a rest. The propeller assembly was taken to Hartzell Propeller Inc for examination with a Hartzell Propeller representative. The examination revealed that both propeller blades appeared to be in a high pitch position. One of the two blades was intact and exhibited extensive spanwise scoring, along with chordwise/rotational scoring near the blade tip. The other blade was fractured about 24 inches from the blade butt. The propeller hub was disassembled and the blades were removed. The pitch change knob on the fractured blade was bent, and the pitch change knob on the intact blade was fractured. The fracture surface of the fractured propeller blade was examined and it exhibited fatigue failure characteristics that originated in a stress raiser located about 1.25 inches from the leading edge on the lower blade surface. A witness mark, in the form of a distinct score line, was present at the fatigue origin site. The airplane's most recent maintenance was an annual/100 hour inspection that occurred on August 21, 2014 at a tach time of 2,096 hours, and a propeller total time in service of 2,049 hours. During the inspection, the leading edges of the propeller blade were filed.