Estimation of Source Rupture Process and Strong Ground Motion Simulation of the 2002 Denali, Alaska, Earthquake

by Kimiyuki Asano, Tomotaka Iwata, and Kojiro Irikura

Abstract

A M_W 7.9 inland crustal earthquake occurred in the Denali fault system, Alaska, on 3 November 2002 at 22:12 (UTC). In this study, we estimated the source process of the 2002 Denali earthquake by a multiple time-window linear kinematic waveform inversion using strong motion and Global Positioning System (GPS)-measured static displacement data.

The obtained source model could explain both the observed strong motion waveforms and GPS-measured static displacements. Large slips on the fault plane are observed at approximately 80–90 km and 150–200 km east from the hypocenter. These features are consistent with the observed surface rupture distribution and the other inversion results obtained using teleseismic body waves. We also observed some portions of the whole fault with a local rupture propagation velocity of more than 4.0 km/sec that exceeded the shear-wave velocity of the source region. The relation between the rupture area and seismic moment of this earthquake seems to follow the bilinear L-model scaling rather than the self-similar source scaling model. The combined area of asperities is somewhat smaller than that expected from the empirical scaling relationship with seismic moments developed by compiling inverted source models.

Finally, we conducted a forward ground motion simulation using the finite difference method to estimate the influence of the heterogeneous source process obtained here on the spatial distribution of strong ground motions. The calculated ground motions are relatively large above and around the large slip areas and also in the region east of the fault area because of the forward directivity effect of unilateral rupture propagation.

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