Summary

Seismograms of more than 100 deep-focus earthquakes originating at epicentral distances from 1° to about 30° from Huancayo, Peru, and recorded there, are used in an investigation of unexplained phases. Three groups of waves, following P after about 5, 10, and 20 seconds, are possibly waves which have changed from longitudinal to transverse at depths of roughly 40, 80, and 150 km., respectively. Other phases may be waves reflected at a depth of between 900 and 1,000 km. The possibility of a sudden small decrease in wave velocity there is discussed. Other observed unexplained phases are mentioned. Reasons are discussed for usually minor disagreements between observed and calculated times, as well as amplitudes of phases in seismograms.

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