abstract

To identify small, deep earthquakes in South America quadripartite nets of about one km in size were set up in Toconce, Chile and Cuzco, Peru. During the period of observation the U. S. Coast and Geodetic Survey identified two fairly large, deep earthquakes in northern Argentina within about a month by teleseismic observations, but neither foreshocks nor aftershocks associated with these earthquakes during the period of observation may indicate that there are comparatively few small, deep earthquakes as compared with shallow earthquakes.

In Toconce, at the foot of the Andes, there was a systematic azimuthal distortion in apparent velocity and in direction of propagation, whereas in Cuzco, on the Altiplano, such a distortion was not found.

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