Spectral Analysis of Earthquake Migration in South America
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Earthquake migration along linear seismic belts is investigated by analyzing space-time diagrams using spectral analysis. In order to sample the earthquakes in the space-time domain, they must first be convolved with a (sin x sin t)/xt surface to obtain an unbiased and alias free two-dimensional Fourier spectrum. Further enhancements are provided by selectively stacking patterns (a pattern is defined as the distribution of earthquakes in space and time before a particular earthquake), thereby reinforcing the similarities within the various patterns. With these techniques, it is possible to quantitatively estimate the migration rates (from their spatial frequencies) and recurrence intervals (from their temporal frequencies) of large earthquakes in South America.
Preliminary examination of the spectra for South America indicates that a low frequency peak occurs at approximately 2500 km and 27 years for earthquakes with magnitudes greater than 7.7. The results suggest a migration rate of approximately 95 km/yr from south to north and a recurrence interval of 27 years.
Key wordsEarthquake prediction Earthquake migration Tectonics South America
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