Summarizes the data on the Lg phase, a seismic wave-train with periods between 0.5 and 6 sec transmitted in the continental crust with a group velocity of 3.44 to 3.57 km/sec, propagating in the Soviet Union and nearby areas. Amplitude-distance curves and amplitude-distance correction factor data used in determining the magnitudes of Lg are given. The available travel time data, including the "standard" travel times of Lg, are summarized. Analysis of the efficiency of propagation of Lg by Soviet seismologists shows that Lg propagates efficiently across the Indian shield, Tarim basin, and the Russian, Siberian, and Kazakh platforms. It propagates less efficiently along Tien Shan and the Himalayas. The Tibetan platform, central part of the Black Sea, and central and eastern parts of the Caspian Sea completely eliminate Lg.
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