Dictionary:Plus-minus method

{{#category_index:P|plus-minus method}} A refraction interpretation method using reversed refraction profiles, also called Hagedoorn method. Let t_AB be the surface-to-surface time between A and B and let t_A and t_B be arrival times at various intermediate locations from sources A and B, respectively. ‘‘Minus’’ values, t_A–t_B–t_AB, are calculated for each location and plotted to give the velocity of the refractor. ‘‘Plus’’ values, t_A+t_B–t_AB, are calculated for each location and plotted to give a picture of the refractor’s depth. See Hagedoorn (1959) or Sheriff and Geldart (1995, 442–443).