Numerical Modeling of Near Fault Seismic Ground Motion for Denali Fault

Tectonic Setting and Fault Motion

The seismic activity in Alaska results due to the interaction between the Pacific Plate and the North American Plate. This collision results in the subduction of the Pacific Plate beneath continental Alaska and the Aleutian Islands. A right-lateral strike-slip fault accommodated this motion along the south-east of Alaska, which caused the 1964 Alaska earthquake (M9.2). It was the largest inland event ever recorded in central Alaska (Eberhart-Phillips et al., 2003).

The mainshock originated about 20 km towards east of the foreshock on the north-dipping Susitna Glacier reverse fault. The strike and dip angles of Susitna Glacier fault were 262⁰ and 48⁰, respectively. The strike angle of Denali fault was 102⁰ with 90⁰ dip. Initially, the rupture started with thrust fault on a 48 km Susitna Glacier fault, and the scrap height measured was about 4.0 m. Later it propagated along 226 km Denali fault, and the average and peak slips were 2.14 and 9.94 m (Dreger, 2003). Finally, it terminated after another 66 km along the Totschunda fault with an average slip of 1.7 m (Haeussler et al., 2004). Figure 1 shows the location of the Denali fault and the epicenter of the 3 November 2002 Denali earthquake.

Figure 1.

Location of Denali fault and epicenter (denoted with star) of 3 November 2002 Denali earthquake