We use the
modified version on the crosscorrelation method
(Tibuleac and Herrin, 1997) to determine the phase velocity and azimuth of the Pg seismic
phases. Waveforms are filtered between 0.6 - 4.5 Hz.
The arrival times for Pg and Lg phases are determined with
wavelet transform methods (Tibuleac and Herrin, 1999) applied on raw data.
The epicentral distance is determined with the formula:
d (km) = 7.84* delta_t(Lg - Pg);
where delta_t(Pg-Lg) is the time difference between the Pg and Lg
arrivals. This formula was calculated using a group velocity of 6 km/s for
Pg and 3.4 km/s for Lg.
Tibuleac, I. M. and E.T. Herrin, (1997), "An Automatic Method for
Determination of Lg Arrival Times Using Wavelet Methods",
Seismological Research Letters, 70, 577 - 595
Tibuleac, I. M. and Herrin, E, (1997), Calibration Studies at TXAR,
Seismological Research Letters, 68, 353-365
Denny, M. D. et al. , (1987), Investigation of mb and Ms formulas
for the Western United States and their impact on the Ms/mb discriminant,
Bull. Seis. Soc. Am., 77, 987-995.