Authors: R Mjelde S Kodaira P Digranes H Shimamura T Kanazawa H Shiobara E W Berg O Riise
Publish Date: 2014/03/16
Volume: 149, Issue: 4, Pages: 641-665
Abstract
—Semiregional Ocean Bottom Seismograph OBS data acquired in the central and northern part of the Vøring Basin midNorway margin have been modeled by use of 2D raytracing The semiregional model derived from the study of twentyfive OBSs deployed along a 120km long profile is compared with a regional model consisting of five OBSs from the same profile The semiregional model is somewhat more detailed than the regional model due to the considerably closer receiver spacing The overall geometry and velocity distribution of the two models are remarkably similar however proving that the regional procedure with large OBS spacing provides a reliable regional model¶Intrusions of sills related to early Tertiary continental rifting and break up are important at intermediate and deep sedimentary levels 2–10 km below sea floor in most parts of the area The semiregional modeling suggests that one of the deepest sills extends much further east and is substantially thicker locally more than 500 m than indicated in the regional model Another important difference is a highvelocity body within the upper crystalline crust at 11–12 km depth in the NW part of the area indicating that the closer OBS spacing in the semiregional modeling allows detection of local intracrustal intrusions Local differences are also inferred in the lower crust at about 20 km depth a structure is inferred within the lower crust from wideangle reflections This might suggest that the highvelocity lower crustal layer interpreted as magmatic underplating consists of a mixture of underplated/intruded magmatic material and blocks of continental lower crust
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