Dissertação (mestrado)—Universidade de Brasília, Instituto de Geociências, 2016. / Submitted by Camila Duarte (camiladias@bce.unb.br) on 2017-02-02T12:05:03Z No. of bitstreams: 1 2016_MarcosViníciusFerreira.pdf: 162813782 bytes, checksum: 51bc6db98418e8499ea885a7391e1017 (MD5) / Approved for entry into archive by Raquel Viana(raquelviana@bce.unb.br) on 2017-02-15T18:13:57Z (GMT) No. of bitstreams: 1 2016_MarcosViníciusFerreira.pdf: 162813782 bytes, checksum: 51bc6db98418e8499ea885a7391e1017 (MD5) / Made available in DSpace on 2017-02-15T18:13:57Z (GMT). No. of bitstreams: 1 2016_MarcosViníciusFerreira.pdf: 162813782 bytes, checksum: 51bc6db98418e8499ea885a7391e1017 (MD5) / A tomografia de ruído ambiental foi utilizada para estudar a crosta e o manto superior sob a porção sudeste da plataforma Sul-Americana. Este método foi escolhido devido à baixa distribuição espacial de eventos sísmicos na região e a dificuldade de obter períodos menores (inferiores a 30 s) para os eventos. Neste trabalho focou-se nas ondas Rayleigh que foram extraídas das Funções de Green obtidas a partir da correlação cruzada de fase (PCC) das componentes verticais dos registros das estações sismográficas. As correlações obtidas foram empilhadas utilizando a técnica do empilhamento de fase com pesos (tf-PWS). Estes métodos realçam sinais fracos aumentando as chances de detectá-los, além de conseguir detectar sinais mascarados por grandes amplitudes e aumentar a razão sinal ruído. Serão apresentados mapas de velocidade de grupo para vários períodos que representam a contribuição de velocidade para profundidades de até 40 km. / The Ambient Noise Tomography technique was employed to study the crust and the shallow mantle under the southeast portion of the South American Platform. This method was chosen due to the poor spatial distribution of ray paths which would be obtained for earthquake surface wave tomography at periods which range from 5s to 20s. In this work, we focus on Rayleigh waves which are extracted from empirical Green's functions which we obtain from the phase cross-correlations (PCC) of vertical component ambient noise recordings. PCC is based on the instantaneous phase coherence of the analytic signals and was chosen since it is amplitude unbiased. The obtained cross-correlations were then stacked using the time-frequency domain Phase Weighted Stacking (tf-PWS). These methods are expected to detect and to enhance weak, but coherent signals concealed in other larger amplitude signals and to improve the signal-to-noise ratio of the final results. Here, we will present group velocity maps several periods which represent the average structure down to depth of about 40 km.