Nontypical BIRPS on the margin of the northern North Sea: The SHET Survey |
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Authors: | Susan McGeary |
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Institution: | British Institutions Reflection Profiling Syndicate, Bullard Laboratories, Madingley Rise, Madingley Road, Cambridge CB3 0EZ, England. |
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Abstract: | Summary. Striking similarities in the reflectivity of the crust and upper mantle on BIRPS profiles has led to the development of the "typical BIRP", a model seismic section for the British continental lithosphere. The SHET survey, collected in the region of the Shetland Islands and the northern North Sea, fits the general pattern to a certain extent. Caledonian structures and Devonian or younger basins are imaged in the otherwise acoustically transparent upper crust. An unexpected and exciting feature imaged on SHET is a short wavelength structure on the Moho or abrupt Mono offset beneath the strike-slip Walls Boundary Fault. SHET differs markedly from the SWAT typical BIRP, however, by showing a poorly reflective lower crust. Only a narrow zone (~1 s) at the base of the crust contains high-amplitude reflections. The SHET survey therefore highlights the wide variation in lower crustal reflectivity within the total BIRPS data set rather than the similarities. |
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