title: Reflection seismology
context: The Canadian inventor Reginald Fessenden was the first to conceive of using reflected seismic waves to infer geology. His work was initially on the propagation of acoustic waves in water, motivated by the sinking of the Titanic by an iceberg in 1912. He also worked on methods of detecting submarines during World War I.  He applied for the first patent on a seismic exploration method in 1914, which was issued in 1917. Due to the war, he was unable to follow up on the idea. John Clarence Karcher discovered seismic reflections independently while working for the United States Bureau of Standards (now the National Institute of Standards and Technology) on methods of sound ranging to detect artillery.  In discussion with colleagues, the idea developed that these reflections could aid in exploration for petroleum.  With several others, many affiliated with the University of Oklahoma, Karcher helped to form the Geological Engineering Company, incorporated in Oklahoma in April, 1920.  The first field tests were conducted near Oklahoma City, Oklahoma in 1921.
question: Who first developed reflection seismology?
answers: 1917