Source Kinematics and Dynamics of the 3 November, 2002 Mw7.9 Denali Fault, Alaska Earthquake

The source kinematics and dynamics of the rupture process of the November 3, 2002 Mw7.9 Denali earthquake is investigated. The epicenter of the event is located near the northern point of the curved Denali fault. The first motion focal mechanism (University of Alaska, Fairbanks), and teleseismic body waves analyzed by Kikuchi and Yamanaka indicate that the event began as a northeast striking reverse fault, and evolved into a 300 km right-lateral strike-slip rupture. Aftershock locations and surface slip observations indicate that the rupture was predominantly unilateral in the eastward direction with the strike of the fault undergoing as much as 40-degree clockwise rotation over the ruptured length. We estimated a seismic moment tensor for the mainshock by inverting long-period waves (100 to 300 sec) recorded at teleseismic distances. A scalar moment of 9.3e20 Nm was obtained, and the focal parameters indicate a strike, dip and rake of 289-degrees, 74-degrees, 148-degrees, respectively. Inversion of displacements from 11 continuous Alaska Deformation Array sites, and horizontal displacement records for the UAF and Anchorage City Hall strong motion sites result in a scalar moment of 6.3e20 Nm. The kinematic inversion results and forward modeling of the strong motion records support the initial reverse motion and overall length of the rupture, however they also suggest that significant slip occurred immediately east of the epicenter; however, it appears to be fairly uniform. Preliminary dynamic modeling using a 2D approximation (no vertical extent) indicates that given the regional tectonic stress field, the central/southeast-striking segment of the Denali fault is most favorably oriented. Furthermore, only a narrow range of stress configurations appears able to produce rupture across the entire fault. The dynamic models indicate that the greatest slip should occur in the central region, which is consistent with the kinematic results of Kikuchi and Yamanaka, our kinematic inversion results and the surface offset data.