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Non-technical summary. The 2002 M=7.9 Denali earthquake, Alaska is the largest earthquake to have struck continental North America since 1857 and one of the largest strike-slip earthquakes globally in historical times. Average surface slip was about 4.5 meters. Global Positioning System (GPS) data recorded in the 2 years since the earthquake reveal that the Earth's crust continues to move at remarkably rapid rates since the earthquake. The fault itself remains locked but the surrounding crust moves in response to relaxation of high-temperature rocks in the mantle (beneath about 40 km depth) generated by the earthquake. In the first weeks after the earthquake, the crust on the two sides of the fault moved up to 400 mm/yr relative to each other, and even one year after the earthquake the relative motion of the crust was up to 150 mm/yr. These rates dwarf the background crustal motions of about 12 mm/yr determined by paleoseismic investigation of the Denali fault. This rapid re-adjustment of the crust after a large earthquake is interpreted using a specialized rheology model of the mantle beneath central Alaska. To explain both the high GPS velocities as well as the sharp decline in velocity after the first few weeks, a" transient rheology" model is introduced. This type of rheology was originally devised to explain laboratory observations of transient creep in metals. It is very effective in predicting the response of the Alaska crust to the stress changes imparted by the Denali earthquake. The importance of transient rheology in governing the behavior of rocks had been predicted already about 25 years ago. However, until the 1999 M=7.1 Hector Mine, California and 2002 Denali earthquakes, it had been difficult to illustrate its importance in practice. If Earth's mantle in earthquake-generating regions is indeed characterized by a transient rheology, then it is not only a useful guide to quantitatively predicting the post-earthquake crustal motions but also provides an analog model for the transition from anelastic to steady state viscous behavior in Earth's mantle.