Geodetic investigation of plate spreading along a propagating ridge: the Eastern Volcanic Zone, Iceland

Abstract

SUMMARY Hotspot-ridge interactions lead to the dynamic evolution of divergent plate boundaries, including propagating and overlapping ridge segments. In southern Iceland, the Eastern Volcanic Zone (EVZ) formed approximately 2–3 Ma ago during the last eastward ridge jump from the Western Volcanic Zone (WVZ), and is propagating to the southwest into the Tertiary lithosphere of the Eastern Volcanic Flank Zone. North America–Eurasia relative plate motion is partitionedbetweentheEasternandWVZs.Weutilizenewterrestrial(dry-tilt)andspace(GPS and InSAR) geodetic data to investigate the nature of plate spreading and magma–tectonic interaction at the southern terminus of this propagating ridge system. We present a new GPS derived horizontal velocity field covering the period 1994–2006, new InSAR analyses for the periods 1993–2000 and 2003–2007, and models of plate spreading across this region. The velocity field indicates horizontal surface deformation consistent with plate spreading across and the propagation of the EVZ. The dry-tilt and InSAR data show transient deformation signals associated with magmatic processes. The velocity field is corrected for these transient deformation sources in order to investigate the nature of secular plate motion. Our model results indicate a decrease in spreading rate from northeast (15 mm yr −1 ) to southwest (9 mm –