Collaborative Research: Tests of Postseismic Deformation Models with Absolute Gravity and GPS Measurements in Alaska

University Of Alaska Fairbanks Campus, Fairbanks AK

Investigators

Abstract

Freymueller 0106829 This project is a test of hypotheses regarding viscoelastic response, aseismic creep, and combinations of both processes following great earthquakes. The collaborative effort, which will take place in Alaska, will make co-located absolute gravity observations (performed by scientists at the University of California, San Diego) and GPS observations (undertaken by scientists at the University of Alaska). Different models of postseismic viscoelastic relaxation predict observable gravity changes over 1000 km length scales, with a complex spatial pattern. To date, the viscosity profile is best determined by postglacial rebound studies. Gravity and GPS measurements offer the opportunity to obtain viscosity profile estimates for the Alaskan plate boundary. The area is especially interesting, as the viscosity of subduction zone materials may be very different from that beneath the centers of continental and oceanic plates. Aseismic creep is predicted to produce deformation of a more limited and markedly different spatial character than that of viscoelastic relaxation. Determining the contribution of aseismic creep in postseismic deformation is important in estimating recurrence intervals for great earthquakes. This project will recover and re-measure previously established absolute gravity stations in Fairbanks and Palmer, Alaska. The two stations are near the minimum and maximum predicted gravity change in the far-field for proposed viscosity models. The measurements are also co-located with existing continuous GPS stations. Comparisons with prior data will be used to test the method, and to provide the basis for model testing.