The Hidden Layer Problem In Refraction Seismic Surveying Dies Hard

A hidden layer is one that lies below a velocity inversion boundary or is<br>a layer that is too thin to be manifested in first arrivals on a refraction<br>record. Since the earliest use of the refraction seismic method, the hidden<br>layer problem has been said to be unsolvable with the refraction data alone.<br>The hidden layer problem actually has two aspects, only one of which is unsolvable.<br>The first aspect, the mapping of the top of the hidden layer, is the unsolvable aspect. The second aspect is the mapping of boundaries below the<br>hidden layer.