Collaborative Research: Mechanisms of Postseismic Deformation Following the 2002 Denali Fault Earthquake Sequence

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Collaborative Research: Mechanisms of Postseismic Deformation Following the 2002 Denali Fault Earthquake SequenceThe occurrence of the Mw 7.9 November 3, 2002 Denali earthquake has created the opportunity to collect the surface deformation measurements needed to make significant improvements in our knowledge of the dominant deformation mechanisms in the Earth's lithosphere and the rheological parameters of the fault zone and surrounding crust and upper mantle. The large moment of the Denali earthquake, the precise pre-earthquake deformation field, and the immediate field response make this the most promising target to address postseismic deformation problems since modern space-geodetic methods became available.Our observational strategy consists of continuous GPS (CGPS) measurements at 16 sites located at a wide range of distances from the rupture, including some at 150 km, in order to distinguish processes in the deep fault zone, the lower crust and upper mantle. Eleven of these sites were installed within two weeks after the event and have since been operating continuously. A fundamental objective of the proposed research is to precisely determine the time-dependence of the postseismic deformation signal. CGPS measurements will be complemented by two GPS campaigns per year, using existing benchmarks, in order to spatially densify the postseismic displacement field. We will also test the ability of InSAR to measure the coseismic and early postseismic deformation.The observational efforts will be complemented by comprehensive modeling efforts to evaluate candidate deformation mechanisms such as velocity-strengthening afterslip, poroelastic rebound, and viscous flow in the lower crust and upper mantle. Characterization of the relative importance of each of these mechanisms is a major goal of this research project. We will fully explore the ability of the different model types (e.g., time-dependent afterslip on and below the rupture vs. powerlaw flow in the lower crust and upper mantle) to fit the data while being consistent with complementary geological and geophysical constraints. PIs: J. Freymueller (Univ. Alaska, Fairbanks), R. Burgmann (UC Berkeley), E. Calais (Purdue University)