Deformation of the Kenai Peninsula, Alaska

Crustal deformation on the Kenai Peninsula in southern Alaska has been studied using data obtained from Global Positioning System (GPS) measurements in 1993 and 1995 and leveling observations in 1964, immediately after the Prince William Sound earthquake. This analysis shows that the Kenai Peninsula has experienced as much as similar to 900 mm uplift during the past 3 decades and that the uplift forms an similar to 125 km wide elongate dome with its major axis trending southwest to northeast following the trend of the major tectonic features of the region. The averaged uplift rate between 1964 and 1995 is as high as 30 mm yr(-1), although the current uplift rate may be substantially lower. The GPS measurements cast further doubt on previously suspect tide gauge data for Nikiski, Alaska, which indicated rapid postseismic uplift at this site located in northwest Kenai Peninsula adjacent to Cook Inlet. Examination of the three-dimensional GPS data indicates that the eastern Kenai Peninsula is currently undergoing significant SSE to NNW contraction in response to North American-Pacific Plate convergence. The horizontal velocities are consistent with the predictions of an elastic half-space model for the interseismic deformation. This result, taken in combination with the small changes in uplift between 1993 and 1995, suggests that most of the present deformation is due to steady plate convergence rather than transient postseismic rebound.