STRAIN ACCUMULATION ALONG THE DENALI FAULT AT THE NENANA RIVER AND DELTA RIVER CROSSINGS, ALASKA

Surveys of trilateration networks across the Denali fault at the Nenana River in 1982, 1984, and 1988 and at the Delta River in 1975, 1979, 1982, and 1984 indicate a minor (0.10 +/- 0.04-mu-strain/yr) northeastward uniaxial extension. The component of right-lateral shear-strain accumulation across the fault is not significant at the two-standard-deviation level. At the Delta River network the strain accumulation rate decreases rapidly with distance from the fault, but evidence for a similar decrease with distance from the fault is lacking at the Nenana River network. The strain accumulation rates inferred from trilateration are consistent with the very long baseline interferometry (VLBI) measurement reported by Ma et al. (1990) and support their contention that significant right-lateral shear is not accumulating along the Denali fault at the present time. Savage et al. (1981) had earlier concluded erroneously that preliminary geodetic measurements at the Delta River network demonstrated right-lateral shear strain accumulation. The absence of significant right-lateral deformation across the Denali fault in the 1975-1988 interval is in marked constrast with the abundant geomorphic evidence for Holocene right-lateral secular slip at the rate of 10-20 mm/yr on the Denali fault in this sector.