| Popis: |
We present a comprehensive average velocity field for Alaska, based on repeated GPS surveys covering the period 1992―2007, and review the major results of previously published papers that used subsets of this data. The spatially and temporally complex pattern of crustal deformation in Alaska results from the superposition of several processes, including postseismic deformation after the 1964 earthquake, spatial variations in plate coupling/slip deficit, translation and rotation of large crustal blocks or plates, and a large slow-slip event in Cook Inlet. Postseismic deformation from the 1964 earthquake continues today, mainly caused by viscoelastic relaxation, and causes trenchward motion. The behavior of the shallow seismogenic zone along the Alaska-Aleutian megathrust is characterized by dramatic along-strike variability. The width of the inferred seismogenic zone varies over along-strike distances that are short compared to the width. The along-strike distribution of locked and creeping regions along the megathrust is consistent with the persistent asperity hypothesis. A large slow-slip event occurred in upper Cook Inlet in 1998―2001, and a smaller event in the same area in 2005―2006. No sign of slow-slip events has been found in segments that are dominated by creep, which suggests that creep there occurs quasi-statically. The overriding plate in Alaska is subject to considerable internal deformation, and can be described in terms of the independent motions of at least four blocks: the Bering plate, the Southern Alaska block, the Yakutat block, and the Fairweather block. |
