A Procedure for the Extraction of Multiple Body Wave Traveltimes From Seismological Waveform Data

Abstract

A scheme for extracting multiple phase body wave traveltimes is presented which is most applicable to teleseismic broadband and short period data from permanent and portable instruments. The method specifically allows for the nonlinear dependence of waveforms on travel time by performing a nonlinear search over a reduced set of “projected model parameters”. This reduced set is found by splitting the method into two parts, the nonlinear dependence of waveforms on traveltime perturbations (particularly strong for broadband and short period data) and the linearizable dependence of travel time perturbations on variations in seismic velocity. By use of generalized inverse, the traveltime perturbations can be adequately characterized by a reduced number of linear combinations of model parameters. Consequently, the nonlinear search is performed over an optimally compact model space. The technique can consider simultaneously a large number of body wave phases creating a systematic methodology for extracting large numbers of traveltimes from single source-receiver pairs. The resulting path model may or may not be of physical significance; the primary goal is the extraction of travel times that may be subsequently used for a more comprehensive travel time inversion.