Source mechanism of the Alaskan earthquake of 1964 from amplitudes of free oscillations and surface waves

Abstract

Spectral amplitudes of Love and Rayleigh waves in the period range 100–300 s and line spectra of toroidal and spheroidal eigenvibrations with periods of 450–800 s ( l = 7 to 17) were used to derive the source mechanism of the Alaskan earthquake of March 28, 1964. It was found that the data are consistent with a dominant dip-slip motion ( λ = 77°–95°) on a steeply dipping fault ( δ = 70°–88°) with a depth dependent source dislocation U 0( h) that extends to a depth of some 125 km [ U 0(0) = 5 m, U 0 (65 km) = 40 m, U 0 (125 km) = 0]. Other source parameters are b = 650 ± 50 km, ν = 3 ± 0.25 km/s, Ω = 3000 μ m and < P> = 1600 unit faults.