Ambient noise tomography reveals upper crustal structure of Icelandic rifts

Green, Robert G. and Priestley, Keith F. and White, Robert S. (2017) Ambient noise tomography reveals upper crustal structure of Icelandic rifts. Earth and Planetary Science Letters, 466. pp. 20-31. ISSN 0012-821X DOI 10.1016/j.epsl.2017.02.039

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Official URL: http://www.sciencedirect.com/science/article/pii/S...

Abstract

The structure of oceanic spreading centres and subsurface melt distribution within newly formed crust is largely understood from marine seismic experiments. In Iceland, however, sub-aerial rift elevation allows both accurate surface mapping and the installation of large broadband seismic arrays. We present a study using ambient noise Rayleigh wave tomography to image the volcanic spreading centres across Iceland. Our high resolution model images a continuous band of low seismic velocities, parallelling all three segments of the branched rift in Iceland. The upper 10 km contains strong velocity variations, with shear wave velocities 0.5 km s−1 faster in the older non-volcanically active regions compared to the active rifts. Slow velocities correlate very closely with geological surface mapping, with contours of the anomalies parallelling the edges of the neo-volcanic zones. The low-velocity band extends to the full 50 km width of the neo-volcanic zones, demonstrating a significant contrast with the narrow (8 km wide) magmatic zone seen at fast spreading ridges, where the rate of melt supply is similarly high. Within the seismically slow rift band, the lowest velocity cores of the anomalies occur above the centre of the mantle plume under the Vatnajökull icecap, and in the Eastern Volcanic Zone under the central volcano Katla. This suggests localisation of melt accumulation at these specific volcanic centres, demonstrating variability in melt supply into the shallow crust along the rift axis. Shear velocity inversions with depth show that the strongest velocity contrasts are found in the upper 8 km, and show a slight depression in the shear velocity through the mid crust (10–20 km) in the rifts. Our model also shows less intensity to the slow rift anomaly in the Western Volcanic Zone, supporting the notion that rift activity here is decreasing as the ridge jumps to the Eastern Volcanic Zone.

Item Type: Article
Uncontrolled Keywords: 2017AREP; IA72;
Subjects: 02 - Geodynamics, Geophysics and Tectonics
Divisions: 02 - Geodynamics, Geophysics and Tectonics
07 - Gold Open Access
Journal or Publication Title: Earth and Planetary Science Letters
Volume: 466
Page Range: pp. 20-31
Identification Number: 10.1016/j.epsl.2017.02.039
Depositing User: Sarah Humbert
Date Deposited: 08 Feb 2017 10:50
Last Modified: 23 Mar 2017 11:46
URI: http://eprints.esc.cam.ac.uk/id/eprint/3818

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