Spatial interference, reflection character and the structure of the lower crust under extension. Results from 2-D seismic modelling.

It has been noticed that the lower crust appears more reflective (containing flatter, longer and more continuous reflections) on profiles that run along the strike of upper crustal extensional structures than on the orthogonal dip lines. This must be due to greater spatial interference along the dip lines and more out-of-plane reflections along the strike lines, suggesting that the lower crustal structures are elongated at right-angles to the extension direction. This is interpreted to support the view that the lower crust reflections seen in extensional settings are from ductile and perhaps anastomosing shear zones.-from Author