Attenuation of seismic waves in the Trinidad and Tobago area

The attenuation of seismic waves from earthquakes located within the area bounded by 9-12°N and 60-63°W was estimated from short-period seismograms. Coda- Q, Qc, determinations were made for each of the six seismograph stations within the area, while spectral Q values from P-phases, Qα, were estimated for station TRN. The S-S single-scattering model was assumed for coda generation, and the ω-2 source model was assumed for the spectral Q determinations. The Qc values show a strong frequency dependence in the frequency range 1.5-12 Hz. The value of Q at 1 Hz, Qo, was found to lie within the range 107-132, while the rate of frequency dependence, n, extends from 0.80 to 1.06 for shallow events. For intermediate-depth events, Qo varies from 101 to 173 and n from 0.80 to 1.02. The Qα values obtained show a spatial variation within the region, the highest attenuation was obtained on land Trinidad.