Algunas características espectrales de la sismicidad asociada a la actividad del Volcán de Colima

Abstract

A temporary network of digital, three component seismographs was installed from 5th to 15th March in order to monitor the seismicity associated to the activity of the Colima volcano. The events recorded during these ten days were classified by their waveform and/or direct field observations. All the events were analyzed in the frequency domain using FFT to compute Fourier spectra, which wcre corrected for si te effects. Four differcnt typcs of events were observed: B low and high frequency, harrnonic tremors and avalanche trcmors. Spectra of type B high frequency events show a miximum at 5 Hz, whereas type B low frequency
events show a clear peak at 2 Hz, with a characteristic shape. Harmonic tremor spectra show two well defined peaks, but at frequencies that vary between 3 and 1 O Hz. Wc note that the frequency of occurrence of the second peak, of lower amplitude, is always double that of the main peak. Finally, avalanche tremors show a single maximum at 3 Hz, with frequency content distributed in a wider band than that of the preceding types.