Tuesday,
November 29, 2005, 12:15 p.m. GWC 604
Wolfgang Stefan
Dept. Math. & Stats.
Signal Restoration through Deconvolution applied to Deep Mantle Seismic Probes
Abstract
In this study we present a method of signal restoration to improve
the signal to noise ratio, sharpen seismic arrival onset, and act as
an empirical source deconvolution of specific seismic arrivals.
Observed time series g_i are modeled as a convolution of a simpler
time series f_i, and an invariant point spread function (PSF) h
that accounts for the blurring effect of the wave path. The method
is used on the shear wave time window containing SKS and S,
whereby using a Gaussian PSF produces more impulsive, narrower,
signals in the wave train. The resulting time series facilitates
more accurate travel time estimation of the individual seismic
arrival onsets. We demonstrate the success of the reconstruction
method on synthetic seismograms, where sharper onsets of arrivals
facilitate more accurate and objective determination of travel times
of individual phases. The method is also used on real data where
clean and sharp reconstructions are obtained, even for signals with
relatively high noise content. Some of the data highlight how this
approach can be employed to reveal details of the signal that are
not readily apparent in raw waveforms. In particular, we show that
two phases, that traverse the lowermost mantle and arrive nearly
coincident in time near 88-92 degrees in epicentral distance
(S_{ab} and S_{cd}), can be identified in the deconvolved traces
by a systematically broadened pulse shape.
For further information please contact:
mittelmann@asu.edu