Extracting reliable P-wave reflections from teleseismic P wave coda
autocorrelation
Abstract
Recently, many studies have demonstrated the use of teleseismic P wave
coda autocorrelation for imaging lithosphere structures. However, the
reliability of the extracted reflections remains uncertain and a means
of evaluation is lacking. In this paper, we propose a velocity analysis
method that conveniently solves this problem in place of a synthetic
experiment. This method considers the average velocity used for the
horizontal slowness correction as an unknown quantity, and then uses the
continuously varying average velocity for the horizontal slowness
correction. Finally, this method obtains a stacked result that varies
with the average velocity and the vertical two-way travel time to
produce a va−t0 diagram. This method is similar to the velocity analysis
method used in exploration geophysics. In this diagram, reliable
reflections correspond to focused energy clusters, while noise lacks
this feature. Therefore, this method helps determine which reflections
are reliable, while also finding the appropriate parameters for data
processing. Synthetic data tests were performed to demonstrate the
validity of this method, as well as a test of field data for station
BOSA, which illustrates the successful application of the method in the
case of a sharp and flat Moho discontinuity. Finally, we applied the
method to the NCISP-6 dense array, and observed obvious energy clusters
representing reflections from the Moho discontinuity in the results of
most stations. The depth and shape of the Moho discontinuity determined
by this test is consistent with receiver function results, which
verifies the robustness of this method in relatively complex
applications.