HR: 1330h
AN: T52B-0264    [PDF]
TI: GPS Velocity Field in the Nicaraguan Forearc: Results from 2000-2003
AU: * Turner, H L
EM: hturner@uark.edu
AF: Department of Geosciences, University of Arkansas, Fayetteville, AR 72701 United States
AU: La Femina, P C
EM: plafemina@rsmas.miami.edu
AF: RSMAS, University of Miami, Miami, FL 33149 United States
AU: Saballos, A
EM: asaballos.gf@ineter.gob.ni
AF: Direccion de Geofisica, INETER, Managua, 2110 Nicaragua
AU: Mattioli, G S
EM: mattioli@uark.edu
AF: Department of Geosciences, University of Arkansas, Fayetteville, AR 72701 United States
AU: Jansma, P E
EM: pjansma@uark.edu
AF: Department of Geosciences, University of Arkansas, Fayetteville, AR 72701 United States
AU: Dixon, T H
EM: tdixon@rsmas.miami.edu
AF: RSMAS, University of Miami, Miami, FL 33149 United States
AB: Oblique convergence between the Cocos and Caribbean plates along the Middle America Trench has been indicated by several studies. Partitioning of strain/slip between an arc-normal component and an arc-parallel component has been proposed as a consequence of the obliquity of the convergence direction, resulting in northwest directed translation of a forearc sliver. We present results from the first detailed GPS geodetic survey of surface velocities in the Nicaraguan forearc. A network of 12 campaign sites in the forearc region and 4 campaign sites in the backarc region was established in late 2000/early 2001. Eleven of these sites were reoccupied in August 2002 and the entire network was reoccupied in February 2003. Data from 5 continuously operating GPS sites in the Central America region were also analyzed for this project. The observed horizontal velocities for campaign sites in the Nicaraguan forearc have an average magnitude of 15.7 $\pm$ 4.0 mm/yr with azimuths ranging from $\sim$ $280\deg$ to $\sim$ $325\deg$ in close agreement with the value of 14 $\pm$ 2 mm/yr to the northwest predicted by DeMets (2001). The observed horizontal velocities for campaign sites in the near backarc region are also directed to the northwest, but the average magnitude of these velocities is only 2.6 $\pm$ 1.8 mm/yr; essentially near zero within error. The continuous GPS site MANA is located along the arc and has a northwest directed velocity of 8.4 $\pm$ 2.4 mm/yr; intermediate in magnitude between the forearc and backarc sites; lending robustness to the campaign veloctiy solutions. The surface veloctiy field observed in the Nicaraguan forearc strongly supports the previously proposed northwest-directed movement with respect to the stable Caribbean plate of the forearc sliver models and is indicative of strain/slip partitioning along this section of the Middle America Trench.
DE: 1206 Crustal movements--interplate (8155)
DE: 1208 Crustal movements--intraplate (8110)
DE: 8107 Continental neotectonics
DE: 8158 Plate motions--present and recent (3040)
SC: Tectonophysics [T]
MN: 2003 Fall Meeting