Abstract

This paper investigates the kinematics of the rupture process of the main event of the Mw 7.9 Denali, Alaska, earthquake of 3 November 2002. A newly devised hybrid blind deconvolution method is applied to deconvolve teleseismic broadband S-wave displacement recordings of the earthquake so as to determine the apparent source time functions (ASTFs) at 10 stations located around the epicenter. The derived azimuthal angle of slip strongly indicates that the event ruptured unilaterally in an east-southeasterly direction. As determined by the calculated ASTFs, the total duration of the rupture process was about 74 sec. Based on the images of the static slip distribution, three slip-concentrated areas were located at depths of less than 10 km. Maximum slip was about 13.4 m centered at 170 km east of the hypocenter, and the average slip on the observed rupture area reached 4.1 m. One concentrated rupture velocity area, located at 160–180 km east of the hypocenter, coincided with a slip-concentrated area of maximum slip amplitude, strongly suggesting that seismic energy was released rapidly. A region of the fault, along the strike direction, with high rupture velocity (∼80–120 km) also had very low levels of slip, indicating that this portion of the fault may well have been relatively weak. Maximum and minimum rupture velocities were respectively 3.32 and 2.64 km/sec, while the average rupture velocity was about 2.95 km/sec. Based on the average rupture velocity and the source duration, it is suggested that the principal rupture length of the Denali fault must have been greater than 210 km.

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