Abstract: A diastrophism detection method and an apparatus therefor are provided which is capable of predicting a position of occurrence of diastrophism such as an earthquake or the like, a scale thereof, time thereof and the like with increased accuracy without being affected by various artificial and natural noises and being effectively put to practice utilizing a simple and objective judgment procedure and by means of equipments simplified in structure and reduced in cost. A VHF radio wave beyond a line-of-sight distance through a plasma density distribution abnormality zone temporarily formed in the ionosphere during diastrophism such as an earthquake or the like is detected in the form of abnormal propagation, resulting in a position of diastrophism below the plasma density distribution abnormality zone, a scale thereof, time thereof and the like being judged.