FY 2004
Active deformation of the Gorda plate: Constraining deformation models with new geophysical data
Chaytor, J.D., C. Goldfinger, R.P. Dziak, and C.G. Fox
Geology, 32(4), doi: 10.1130/G20178.2, 353–356 (2004) |
| The Gorda plate, the southernmost fragment of the larger Juan de Fuca plate system, is an example of a nonrigidly deforming tectonic accommodation zone or buffer plate, absorbing deformation and allowing the surrounding larger plates to act in a more rigid fashion. Here we present a new structural analysis of the plate based on full-plate bathymetric coverage, augmented by seismic reflection data and earthquake moment tensors and locations. We interpret internal deformation of the Gorda plate as an asymmetrical flexural-slip buckle with a vertical axis, utilizing reactivation of spreading-ridge fabric normal faults as strike-slip faults. Newly formed second-generation faults crosscutting the structural grain overprint the reactivated structures. The spreading fabric faults finally begin a second phase of extension as the plate approaches the subduction zone. This model, based on fault constraints, has allowed investigation of ridge-plate–subduction interactions, and suggests that spreading-rate variations along the Gorda Ridge may be controlled by internal deformation of the plate rather than the reverse, as previously hypothesized. |
