HR: 08:45h
AN: S11B-02 INVITED     [PDF]
TI: Surface rupture and revised slip distribution on the Denali and Totschunda faults from the M 7.9 Denali fault earthquake
AU: * Haeussler, P J
EM: pheuslr@usgs.gov
AF: U.S. Geological Survey, 4200 University Dr., Anchorage, AK 99508 United States
AB: We revised the preliminary slip distribution (Science, 2003, v. 300, p. 1037ff) along the Denali and Totschunda faults after additional fieldwork this summer. Features of the surface trace had degraded in places due to melting of snow, permafrost, and soil. However, without snow cover, offset of fine-scale features was much clearer at many new localities. We were also able to add additional measurements on glaciers, where offset snow-filled crevasses could be observed. As a result, the revised slip distribution provides considerably more detail and a higher level of confidence than that inferred solely from measurements collected immediately after the earthquake. The primary features of the revised slip distribution are: 1) a broad plateau of roughly 5-m offsets extending from 70 to 170 km east of the epicenter along the central part of the Denali fault, 2) high-slip values of 6.5-8+ m between 170 and 212 km east of the epicenter, 3) the step up from the 5 m plateau to the higher is sharp, occurring over a lateral distance of one kilometer, 4) there are three new, and anomalously high, measurements of 7.2-8.2 m along a 7-km length of the fault within the plateau of 5-m slip values, 5) there was a maximum 3-m offset on the Totschunda fault, which is 0.9-m higher than previously measured; 6) A previously inferred region of high slip in the vicinity of the Trans Alaska Pipeline is less obvious or absent. However, slip in that area is higher than the region to the west of the Delta River, 7) In contrast to geodetic and seismologic slip models that infer low slip and moment release in a zone 100-160 km east of the epicenter, we find continuous surface offsets of about 5 m; 8) A drop to zero slip, previously inferred at the Totschunda-Denali junction appears to be a result of slip values obtained from transfer structures. The smallest robust measurements of lateral slip in the transition zone were about a meter. Denali Fault Earthquake Geology Working Group : T. Dawson, P. Haeussler, J. Lienkaemper, A. Matmon, D. Schwartz, H.Stenner, B. Sherrod (USGS), F. Cinti, P. Montone (INGV, Rome)
DE: 1242 Seismic deformations (7205)
DE: 7209 Earthquake dynamics and mechanics
DE: 7215 Earthquake parameters
DE: 8123 Dynamics, seismotectonics
SC: Seismology [S]
MN: 2003 Fall Meeting