EXERCISES USING THE CONSTANT-SPEED METHOD 1. Although the epicenter may be located with three seismic stations that record the same earthquake, a fourth one has been used here to verify your findings. Four partial records of the same earthquake were recorded at Los Angeles, San Francisco, Salt Lake City, and Albuquerque, shown below. Determine the lag time for each recording station and enter it into the "lag time" column, by subtracting the P-wave arrival time from the S-wave arrival time