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The Great M7.9 Denali Fault, Alaska, Earthquake of November 3, 2002: Geotechnical Engineering Reconnaissance

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Introduction
Following the Mw 7.9 earthquake we conducted a reconnaissance of the region to investigate geotechnical engineering features of the event. The focus of our investigation was to characterize the spatial extent and amplitude of ground failures and assess damage to structures. The most noteworthy aerial observations were that geotechnical and structural damages appeared to be focused towards the eastern end of the Denali-Totschunda fault rupture area. Sparse sand vents and lateral spreads on bars of the western Tanana River, from Fairbanks to Delta, became pervasive to the east. Likewise, for the four glacier-proximal rivers draining toward the north, little or no liquefaction was observed on the western Delta and Johnson Rivers whereas, the eastern Robertson and Tok Rivers and, especially, the Nabesna River had observable-to-abundant fissures and sand vents. Ice on frozen lakes and ponds was shattered within about 30-40 km of the fault along the western part of the surface rupture and to the east became more widespread. In the Northway region ice on most lakes was broken at distances of more than 100 km.
Map of Denali Fault reconnaissance area.

Click on map for larger image (88K)

Where the fault crossed the trans-Alaska pipeline strong shaking, inertial motions, and permanent offset of the fault beneath the pipe resulted in damage to 8 horizontal support members, and 9 anchored supports near the fault crossing. The pipe is free to slide on Teflon skids and in numerous locations, especially south of the fault, the pipe collided with vertical support members (VSM). These affects were not critical to the integrity of the pipeline, which performed well during the event.

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last modified 1 December 2003 (lzt)
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