9706318 Freymueller This research will address two important problems in the active tectonics of Alaska, the slip rate on the Denali fault, and the relationship between the Denali fault and zones of active seismicity to the north. Past measurements of the slip rate on the Denali fault are in conflict. Line length measurements from 1975-1988 showed barely significant right lateral shear strain in two networks crossing the Denali fault, yet geologic estimates of the Holocene slip rate on the Denali fault are 8-12 mm/yr. Seismicity North of the Denali fault is concentrated in NE trending zones, with left-lateral slip on steeply dipping NE to NNE striking planes. These left-lateral, strike-slip faults have been interpreted as secondary faults bounding elongated crustal blocks in a broad shear zone between the Denali and Tintina (right-lateral) strike-slip faults. The PIs will measure the slip rate on the Denali fault and place some initial constraints on the strain rate across the active seismic zones to the north of it, using data from GPS (Global Positioning System) surveys and permanent GPS sites. They will also survey an extensive network across the active seismic zones that can be re-occupied in the future to more fully characterize the active deformation. ***
