Back to Fall 1999 AGU abstract list.
Back to the News
|
Global Positioning System (GPS) Measurements of Convergence at the New Hebrides Island Arc System David A. Phillips 1 (808-956-2360; dap@soest.hawaii.edu) Frederick W. Taylor 2 (fred@utig.ig.utexas.edu) Michael G. Bevis 1 (bevis@soest.hawaii.edu) Stephane Calmant 3 Jean-Michel Bore 3 Douglas Charley 3 Charles Pakoa Eric C . Kendrick 1 1University of Hawaii, Hawaii Institute of Geophysics and Planetology (HIGP), 1680 East-West Road Suite 813, Honolulu, HI 96822, United States 2Institute of Geophysics, University of Texas, 4412 Spicewood Springs Rd Bldg 600, Austin, TX 78759, United States 3Institut de Recherche pour le Développement (IRD), Laboratoire de Geophysique, Centre IRD de Noumea, Noumea, New Caledonia Global Positioning System (GPS) data from the New Hebrides island arc system illustrate the effects of large bathymetric features entering an active subduction zone. GPS measurements made in this region from 1990 to 1992 and reported by Taylor et al. (1995) showed that convergence rates across the southern New Hebrides Trench were higher than predicted by the NUVEL-1A model while convergence rates in the central New Hebrides were dramatically lower than predicted. This abrupt change in convergence rates along the trench strike was attributed to two things: 1) accelerated velocities in the south due to rapid back-arc extension in the North Fiji Basin, and 2) fragmentation of the central arc due to impingement of the D'Entrecasteaux Ridge and associated Bougainville Seamount. Additional GPS measurements have been made since 1996 and the results are presented here. Convergence rates in the southern New Hebrides continue to exceed the predicted NUVEL-1A values while rates in the central New Hebrides are confirmed to be considerably lower than expected. Additional GPS stations were added during the 1996-1999 campaigns in an effort to resolve variations in strain accumulation in the central arc. On the south and east coasts of Espirito Santo, no large changes in strain accumulation were observed from 1992 to 1999. However, approximately 20 mm/yr of strain variation was observed across the Aoba basin, which is greater than predicted by current interseismic strain accumulation models. This may be due to behavior of the back-arc reverse fault where eastward motion of the central arc block is being accommodated. Our new results support the collisional fragmentation model for the Central New Hebrides arc and provide additional information about processes that could potentially result in arc polarity reversal. |
Meeting: Meeting Section: Special Session: Index Terms: Theme: |
Last Modified: October 8, 1999
Comments: UTIG webmaster