Abstract

In 1984 the U.S. Geological Society collected 850 km of refraction data in lines parallel and perpendicular to regional strike of the Appalachian orogen in Maine and southeastern Quebec. A 100-km-long strike-line in coastal Maine, west of Penobscot Bay, is here interpreted on the basis of both refracted and reflected phases. Techniques used in seismic reflection processing, including normal movement velocity corrections and common mid-point stacking, were applied to the refraction data in order to enhance the visibility of reflected phases. The geometries of the most laterally continuous reflections as defined by these techniques can be correlated with reflections seen on a crossing, near-vertical reflection profile. Conventional ray-tracing analysis of refracted and wide-angle reflected phases in the refraction data constrains the velocity structure to about 14 km depth, and provides evidence for high-veiocity material (>6.5 km/sec) between 4 and 7 km depth, and for lower velocities (<6.3 km/sec) from 7 km to at least 14 km depth. The velocity analysis of reflection data, based on single-fold constant-velocity sections and study of common mid-point stacked sections, confirms the existence of this zone of reduced velocity in the crust from 7 to 14 km. The combined refraction/reflection interpretation of this profile, in conjunction with data from crossing refraction and near-vertical reflection lines, provides a velocity and structural characterization of this part of the Maine coast.

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