A study of mantle layering beneath the western Pacific

The reverberative interval of the seismogram, defined as the portion following the surface wave train propagating along the minor arc and ending with the first body wave arrivals from the major arc, provides an excellent window in which to observe reflections from mantle discontinuities. On an SH-polarized seismogram in the intervals between ScS_n and sScS_n wave groups (zeroth-order reverberations) are approximately 15 min long and consist almost entirely of waves reflected one or more times from mantle discontinuities (first- and higher-order reverberations). We have developed signal enhancement and waveform inversion schemes to progressively extract information pertaining to mantle layering from the waveforms of zeroth- and first-order reverberations and have applied them to a data set of long-period digital seismograms drawn from a number of tectonic regions in and around the western Pacific. The results place important constraints on the nature of the transition zone discontinuities. -from Authors