Translations:Dictionary:Blind zone/3/en

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2. A layer that does not give a refraction first break. Also called hidden layer or shadow zone. See Figure H-5. The blind zone (a) may have a velocity lower than that of a shallower refractor, in which case it may lead to overestimating the refractor depth, or (b) it may have a velocity intermediate between those of layers above and below but not have sufficient thickness or velocity difference to produce first arrivals; in which case it is apt to cause underestimating the refractor depth.