ABSTRACT

The group velocities of 91 Lg arrivals at the Dallas Observatory in 1954, 1955, 1956, and 1957 have a mean of 3.468 ± 0.010 km/sec. A t-test shows that Lg waves traveling from Baja California to Dallas have a velocity significantly larger at the 0.999 probability level than those traveling from California to Dallas. Four Lg arrivals which traveled from Mexico to Dallas across the outer continental shelf of the Gulf of Mexico have a mean velocity of 3.22 ± 0.03 km/sec. A table for estimating epicentral distances from P and Lg arrival times is included.

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