After extracting earthquake wave forms from the CMMT and CHTO
stations, the P-wave arrival time of each event was manually chosen
and the waveform was windowed down to 30 s before and 90 s after
the P-wave arrival time. Bad traces were also discarded when choosing
the P-wave signal and during determining the mean and performing
trend removal. The data was then rotated from the conventional Cartesian
N–S, E–W and Z system into the vertical (Z), radial (R) and transverse
(T) coordinate system. The iterative deconvolution technique
(Ligorria and Ammon, 1999) was used to deconvolve the wave forms
in the vertical component from those of the radial and transverse components
to generate the receiver function (Ammon, 1991) under the
criteria that they must fit each other to within at least 85% to ensure a
high quality result. A Gaussian filter with a value of 2.5 was applied to
clean up the high frequency noises roughly above 1 Hz. The processing
was done by the Seismology package of Herrmann and Ammon (2002).
Finally, this left us with 119 and 59 observed receiver function (ORF)
events for the CMMT and CHTO stations, respectively