(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.

Bibliography

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.