Interpretation of the precursor to the 1960 great chilean earthquake as a seismic solitary wave

Seismic solitary waves may exist. The situation envisaged is that of an elastic layer over a half space where transverse, linearly polarized surface waves—Love waves—propagate. In the long wavelength limit, nonlinearities may compensate dispersion so that localized wave packets can propagate without distortion. A model equation is derived that explicitly exhibits this phenomenon, having among its solutions a strain solitary wave. It is predicted that strains of seismic interest should propagate with the shear wave velocity of the underlying half space, and they should have a wavelength about three orders of magnitude greater than the depth of the top layer. In light of the above considerations the precursor to the 1960 great chilean earthquake recorded with the Pasadena strain seismogram is interpreted as a seismic solitary wave produced by the foreshock that preceded the main shock by about 15 min. It traveled as a surface wave guided by the oceanic crust.