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Title: The role of pore pressure diffusion in a reservoir-induced seismicity site in NE Brazil
Author: Do Nascimento, Aderson F.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2002
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From August 1994 until May 1997, a network of 8 three-component digital seismographs operated at the Açu reservoir. A detailed analysis of this data forms the first part of this thesis. The earthquake locations revealed remarkably well-defined NE trending fault structures beneath the reservoir due to the simple seismic-wave velocity structure of the area. This digital data is shown here to be very suitable for focal mechanism determination and also to investigate seismic anisotropy in the area. This is possible due to the low attenuation of the seismic waves and good signal-to-noise ratio in the seismograms provided by the crystalline rocks of the area. The focal mechanism determination and the shear-wave study of this seismicity confirm that the area is in E-W compression and also that the shear-wave splitting is controlled by the seismic anisotropy associated with the Precambrian foliation. Moreover, this study shows that the seismicity migrates between different faults and within individual faults over different time periods. To investigate this behaviour and relate it to changing water levels in the reservoir and the resulting groundwater flow beneath, a fully three-dimensional groundwater flow code (PARADIGM) is used. PARADIGM is employed to simulate the pressure field in both the rock matrix and an idealised fault geometry. This flow modelling forms the second major component of this thesis. The significance of my approach is that I explicitly consider the physical meaning of hydraulic conductivity and storativity and their impact on fluid flow. In this model, both realistic information on the hydrogeological regime of the area and measurements of real fault zone hydraulic properties are included. The combination of the spatio-temporal analysis of the seismic activity and the numerical simulations carried out in PARADIGM provide new insights into the mechanism that causes the migratory behaviour.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available