Article,
Complex polarization analysis of particle motion
Bulletin of the Seismological Society of America, 76 (5): 1393--1405 (Oct 1, 1986)
Abstract
Knowledge of particle motion polarization aids in identifying phases
on three-component seismograms. The scheme of Montalbetti and Kanasewich
(1970) is extended to analytic three-component seismograms, where
the imaginary part of the signal is the Hilbert transform of the
real part. This scheme has only one free parameter, the length of
the time window over which the polarization parameters are estimated,
so it can be applied in a routine way to three-component data. The
azimuth and dip of the direction of maximum polarization and the
degree of elliptical polarization as a function of time for the seismograms
are obtained. Polarization analysis of strong motion data from the
1971 San Fernando earthquake aids in the discrimination between wave
types, which is important for the understanding of the complicated
earthquake-induced shaking observed in basins. Most arrivals are
incident on the receivers in the direction of the back-azimuth to
the epicenter, which suggests that despite the complicated motions,
two-dimensional finite difference methods are sufficient to understand
the effect on seismic waves of the Los Angeles and San Fernando basins
(Vidale and Helmberger, 1986b).
