Crustal structure of the Andes from Rayleigh wave dispersion

Abstract

Records from a Benioff short-period seismograph located at Huancayo, Peru, are digitalized and then passed through a low-pass filter to get the long-period waves. In this way the dispersion curves of Rayleigh waves for paths along the Andes can be computed from seismograms which otherwise would be unusable. The comparison with the empirical curve for a "normal" continental crust (Press 1960) and with specially computed theoretical models indicates a crustal thickness of the order of 50 km. For periods between 20 and 25 sec., the observed group velocity shows abnormally low values.

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