Teleseismic receiver function method
We additionally examine P-wave receiver function (RF) using MASE dataset in support
of the migrated image (Figure 6a), and the method is briefly summarized here. Standard
RF processing emphasizes direct Pds phase by removing source complexity through
the deconvolution of radial component seismograms by corresponding vertical
component seismograms [Langston, 1979]. The amplitudes of the Pds phases primarily
depend on the incidence angle of the impinging teleseismic P wave and the velocity
contrast across the discontinuities. Earthquake sources within 30 to 90 degree distance
ranges with magnitudes greater than 6.0 are used in the analysis. Individual waveform
data are (1) time-windowed to 90 s, (2) band-pass filtered at 0.01–1 Hz for the region
sampling the flat slab subduction (Figure 6b) and 0.03–0.5 Hz for the region beneath
the arc (Figure 6d), and (3) rotated to radial and tangential coordinates. Radial
component seismograms are then deconvolved with vertical component seismograms
at each station using time-domain iterative deconvolution [Kikuchi and Kanamori, 1982;
Ligorria and Ammon, 1999] with a Gaussian filter parameter of 4. We mainly
concentrated on radial RFs in this paper. A detailed analysis of the tangential
component from MASE array for the 550 km transect is given by Greene [2009]. Song
and Kim [2012a; 2012b] also discuss the tangential RFs for the shallow-to-flat oceanic
crust in central Mexico based on the MASE dataset. We note that the 2-D GRT method
relies primarily on the backscattered signals whereas the RF image does not exploit
free-surface multiples, and so there is a large degree of independence between the two
images for a depth less than 60 km [Rondenay et al., 2005].
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