David H. Johnston is Managing Director of Differential Seismic, LLC, a geophysics consultancy. Dr. Johnston retired from ExxonMobil in 2017 after a 38-year career in research, exploration, and production. He was responsible for the development and commercialization of 4D seismic technology in ExxonMobil and was Geophysics Coordinator for ExxonMobil Production Company where he provided technical and business stewardship of ExxonMobil’s global production geophysics activity. He earned a Bachelor of Science degree in earth sciences from the Massachusetts Institute of Technology in 1973 and a Ph.D. in geophysics in 1978, also from MIT. Dr. Johnston has received numerous awards from the SEG and in 2013 he served as the SEG Distinguished Short Course Instructor.