LANDSLIDES TRIGGERED BY THE 2002 M-7.9 DENALI FAULT EARTHQUAKE, ALASKA: INFERENCES ABOUT STRONG SHAKING

The moment magnitude (M) 7.9 Denali Fault, Alaska, earthquake of 3 November 2002 triggered thousands of landslides, primarily rock falls and rock slides, that ranged in volume from rock falls of a few cubic meters to rock avalanches having volumes as great as 15x10⁶ m³. The pattern of landsliding was unusual: the number and concentration of triggered slides was much less than expected for an earthquake of this magnitude, and the landslides were concentrated in a narrow zone about 30 km wide that straddled the fault rupture zone over its entire 300-km length. The large rock avalanches all clustered along the western third of the rupture zone where acceleration levels and ground-shaking frequencies are thought to have been the highest. Inferences about near-field strong-shaking characteristics drawn from interpretation of the landslide distribution are strikingly consistent with results of recent seismological modeling that indicates that high-frequency energy generation was greatest in the western part of the fault-rupture zone and decreased markedly to the east.