E. Del Pezzo, M. La Rocca, and J. Ibanez
Observations of high-frequency scattered waves using dense arrays at Teide Volcano
Bulletin of the Seismological Society of America (December 1997), 87(6):1637-1647

Abstract:
A study of the seismic coda of seven small earthquakes recorded on the Teide Volcano-Canary Islands (Spain) was carried out using a temporary, small-aperture, 12-station, seismic array. The purpose was to measure backazimuth, apparent velocity and the type of waves that compose the coda in the frequency range 4 to 6 Hz. We used the zero-lag cross-correlation (ZLC) method to obtain the components of the wave vector and three-component analysis techniques based on the covariance matrix of the signal in the time domain to investigate the polarization properties of the signals. The results show that a great part of the coda signals in the analyzed frequency range are almost uncorrelated, while a low number of isolated correlated arrivals show an apparent slowness between 2X10 (super -3) and 2.5X10 (super -4) sec/m and an almost random distribution of backazimuths. The correlated arrivals have been interpreted as generated by strong scatterers, probably related to the presence, in the study area, of surface topography irregularities (the volcanic cone and the caldera rim). The wave type varies from pure S-type waves to mixed surface waves with some Rayleigh components.