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The crustal structure of the Reykjanes Ridge at 59° 30'N |
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| Authors: | A W H Bunch B L N Kennett |
| Institution: | Department of Geodesy and Geophysics, University of Cambridge, Madingley Road, Cambridge CB3 OEZ;Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Silver Street, Cambridge CB3 9EW |
| Abstract: | Summary. In order to examine the development of the oceanic crust in the neighbourhood of a slowly spreading ridge, a seismic refraction experiment was carried out at 59° 30'N on the Reykjanes Ridge. Three 120 km long overlapped split profiles were shot parallel to the trend of the ridge, on the eastern flank, and recorded on up to five recording sonobuoys. The profiles were at distances of 0, 30 and 90km from the ridge axis, corresponding to approximate crustal ages of 0, 3 and 9 Myr. Data from the main profiles were supplemented by using a large chamber air gun during recovery of the buoys. The analysis of the data combined standard travel-time interpretation, the 'tau' method of systematic travel-time inversion and detailed amplitude modelling using the Reflectivity Method to calculate synthetic seismograms. Detailed velocity-depth models were constructed for each of the profiles. There is no indication of a significant magma chamber at the ridge crest, although a slight velocity inversion in layer 3 suggests a zone of elevated temperature. Away from the crest there was a slight positive velocity gradient in layer 3. Layer 2 was most effectively modelled by a region of varying velocity gradients, which thinned with age and the transition to layer 3 is marked by a sharp change in velocity gradient. The transition to mantle velocities is also best modelled by a high velocity gradient rather than an interface. Although some lateral variation in properties is apparent along the profiles, the lateral velocity gradients were sufficiently weak to allow an effective analysis in terms of laterally uniform models. |
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