The Great 1964 Prince William Sound, Alaska, Earthquake: Estimation of Strong Ground Motion

Abstract eng:
We are generating physically plausible near-field synthetic ground motions for the Great 1964 Prince William Sound, Alaska, earthquake compatible with available seismological data, tectonic information and eyewitness accounts. The objectives of this study are summarized as follows: (a) Simulation of the low-frequency (f < 0.03Hz) strong ground motions on selected locations and on a dense grid of observation points extending over the shallow dipping causative fault of the 1964 Alaska earthquake. In order to accomplish this task, we are utilizing the slip model proposed by Johnson et al. (1996) based on a joint inversion of tsunami waveforms and geodetic data. The calculations are carried out using the discrete wavenumber representation method and the generalized transmission and reflection coefficient technique; (b) Reconstruction of the strong ground motion time histories and response spectra that the city of Anchorage experienced during the 1964 Alaska earthquake. The low-frequency (f < 0.03Hz) ground motions are generated using the methodology described previously. The intermediate-frequency (0.03Hz < f < 0.50Hz) ground motions are simulated by convolving Green’s functions generated by the discrete wavenumber representation method with far-field radiation pulses of circular cracks. The high-frequency (0.5Hz < f < 8.0Hz) ground motions are simulated using the stochastic modeling approach. The three independently derived ground motion components are then properly combined to generate synthetic broadband ground motion time histories and response spectra for the city of Anchorage due to the 1964 Prince William Sound earthquake; and (c) Validation of the synthetic strong ground motions for the 1964 Alaska earthquake against observed tectonic deformation, ground motion estimates inferred by descriptions of structural damage, and eyewitness accounts. In summary, the present study provides synthetic time histories and response spectra for engineering applications compatible with all available information pertaining to the 1964 Prince William Sound earthquake. It should be noted however that the generated strong ground motions are not necessarily unique, nor reflect the entire uncertainty that characterizes the problem under investigation.

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