12. Surface Wave Dispersion in Brazil East of Andes

by Edward O. Osagie
Benson Idahosa University, Department of Physical Science, Benin City – Edo State

Abstract
This paper presents the results of a study of the dispersion characteristics of fundamental mode surface waves propagating in Brazil, east of Central Andes in particular, the continental crust and upper mantle structure. The occurrence of several large earthquakes in South America from 1965 to 1974 permits a reconnaissance study of the continental crust and upper mantle structure of Brazil, east of the Andes using surface wave dispersion. Data from WWSSN stations NAT and LPA were used to measure fundamental mode group velocity of Rayleigh and Love waves. The average S- velocity in the lower crust was found to be 4.40 km/sec. in Brazil, east of the Andes, which is typical of stable continents. The average S- velocity beneath the upper mantle is 4.66 km/sec, a typical value for cold platform areas. Other seismological data support this observation.

Keywords: Surface waves, dispersion, continental crust, upper mantle, Brazil.