Nonparametric Deconvolution of Seismic Depth Phases

• Activity Number: 191
• Type: Invited
• Date/Time: Tuesday, August 5, 2003 : 8:30 AM to 10:20 AM
• Sponsor: Seismological Society of America
• Author(s): Robert H. Shumway*+
• Companies: University of California
• Keywords: Cepstral F ; array processing ; signal detection ; nuclear monitoring

Abstract

Accurate determination of the source depth of a seismic event is a potentially important goal for better discrimination between deeper earthquakes and more shallow nuclear tests. Earthquakes and explosions generate depth phases such as pP and sP as reflections of the underlying P signal generated by the event. The delay time between the original signal and the pP phase can be used to estimate the depth of the seismic event. Cepstral methods offer natural nonparametric means for estimating general echo patterns in a single series. Here, we extend the single series methodology to arrays by regarding the ensemble of log spectra as sums of nonstationary smooth functions and a common additive signal whose periods are directly related to the time delays of the seismic phases. Plotting an approximate cepstral F-statistic over pseudo-time yields a function that can be considered as a deconvolution of the seismic phases. We apply the array methodology to determining focal depths using three component recordings of earthquakes. The work is joint with Drs. J.L. Bonner and D.T. Reiter of Weston Geophysical Corporation, Northborough, MA.