The Absolute Motion of Trenches and Age of the Subducting Slab
Mathews, David Christopher
Gordon, Richard G
Master of Science
Previous work proposes that many trenches advance, but inferred motions vary considerably between different estimates of plate motion relative to hotspots. We remedy this by using recent estimates of absolute plate motions inferred from seismic anisotropy, incorporating the MORVEL relative plate angular velocities, and fully propagating the uncertainties. Nearly half the trench velocities differ significantly from prior results, with the greatest differences at the Kermadec, New Hebrides, and Marianas trenches. Trench velocity ranges from retreat of 126 ± 20 mm a-1 to advance of 52 ± 14 mm a-1 with a median of 9 mm a-1 of retreat. Out of 57 locations, trench advance is significant at only five locations (along the Hikurangi, Marianas, and Izu-Bonin trenches), retreat is significant at 23 locations, and trench motion differs insignificantly from zero at 29 locations. Trench advance increases with age and absolute velocity of subducting lithosphere and with angle of subduction.
trench advance; slab age; absolute plate motion; plate tectonics