Monitoramento de mudanças de velocidade no Arquipélago São Pedro São Paulo com interferometria de ruído sísmico
The Saint Paul Transform System (SPTS) is located in th MId-Atlantic Ridge (MAR), Equatorial Atlantic and is formed by a multi-fault complex system, where many faults are interacting and small-to-moderate events are routinely located in the area using global seismic networks. This seismicity is c...
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| Formato: | Dissertação |
| Idioma: | pt_BR |
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Universidade Federal do Rio Grande do Norte
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| Endereço do item: | https://repositorio.ufrn.br/handle/123456789/32079 |
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| Resumo: | The Saint Paul Transform System (SPTS) is located in th MId-Atlantic Ridge (MAR),
Equatorial Atlantic and is formed by a multi-fault complex system, where many faults are
interacting and small-to-moderate events are routinely located in the area using global
seismic networks. This seismicity is challenging to charecterize since no permanent seismic
stations near this area is available. As a result, the effect of the seismic events on the
rock mass and the inter-play between seismicity, faulting and fluid in the MAR is poorly
constrained. In this dissertation, we quantify the seismic velocity pertubations due to smallto-moderate magnitude earthquakes in the Saint Peter Saint Paul Archipelago (SPSPA)
using one seismographic station installed in the region. We calculate noise auto-correlation
functions using the data recorded by this station. The auto-correlograms were obtained by
two different approaches: classical auto-correlation geometrically normalized (ACGN) and
phase autocorrelation (PAC). We found that both approaches give very similar results
and we are able to estimate velocity changes due to small earthquakes (between 3.0 and
4.7 ML). The changes in the medium were investigated through the joint analysis of
decorrelation curves and velocity changes obtained by Moving Window Cross Spectral
(MWCS) method. Our analysys show that the velocity changes are possibly associated
with a hydromechanical coupling in which the observed velocity increase is driven by static
stress changes and fluid-rock interaction is responsible for the observed velocit drop. This
behavious is qualitatively explained by the multi-fault complex system nature of the SPTS,
where fluid-rock interaction plays an important role in the observed velocity variation. |
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