Tomografia de ruído sísmico de ambiente na Província Borborema com estações de período curto
Analysis of ambient seismic noise has proved to be a viable alternative to earthquake-generated seismic wave analysis. Although for a long time it was commonly discarded from earthquake recordings, it has been shown that the cross correlation of ambient seismic noise allows the recovery of the Gr...
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Formato: | Dissertação |
Idioma: | pt_BR |
Publicado em: |
Universidade Federal do Rio Grande do Norte
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Endereço do item: | https://repositorio.ufrn.br/handle/123456789/30267 |
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Resumo: | Analysis of ambient seismic noise has proved to be a viable alternative to
earthquake-generated seismic wave analysis. Although for a long time it was
commonly discarded from earthquake recordings, it has been shown that the
cross correlation of ambient seismic noise allows the recovery of the Green’s
function between receivers. Moreover, seismic noise has the property of
propagating uninterruptedly and independently of the occurrence of
earthquakes, allowing for high resolution tomographic studies in low seismicity
regions. Over the past two decades, the correlation of seismic noise between
pairs of seismographic stations has been widely utilized in surface-wave
tomography studies. In particular, for the northeast Brazil region, tomography
studies used temporary and permanent broadband stations to investigate the
deep structure (upper crust) of the Borborema Province; however, in addition
to the broadband stations mentioned above, there is a large volume of data
collected by 22 short-period stations that could improve the resolution of these
tomographic studies. Thus, the goal of this MSc dissertation is to investigate
whether short-period data: (i) can be used in surface-wave tomography
studies, and (ii) can be combined with broadband data in a single tomographic
inversion. Through the cross correlation of the recorded ambient seismic noise
between short-period stations and subsequent stacking, the emergence of the
dispersive, fundamental-mode Rayleigh waves was verified. It was also found
that the dispersion curves (group and phase) could be satisfactorily obtained
for periods of up to 10 s (after removal of the instrumental response), using
standard surface-wave analysis techniques, and that it was indeed feasible to
invert them together with dispersion curves from broadband recordings. The
results obtained in the Borborema Province show that, for the 5 to 10 s period
range, it was possible to define structures such as the Sergipe-Alagoas basin
and the Borborema Plateau, which were not well delineated in previous
tomographic studies. |
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