Tomografia de ruído ambiental: uma contribuição para estimação da estrutura crustal sob a Bacia do Pantanal

Abstract

The crustal structure knowledge of the major part of South America is still low developed. Even in already studied regions, there are low resolution data mostly because seismic tomography limitations and the low density of seismographic stations that could be used in other seismological methods like receiver functions. In this way, the Ambient Noise Tomography (ANT) appears as a good alternative to develop crustal studies in specific intracontinental areas, such as the Pantanal Basin. The Pantanal Basin is constituted by quaternary sediments irrigated by the Paraguai River, with sedimentary thickness of 500m and structured by faults and fractures related to the Transbrasiliano Lineament (TBL). The Pantanal Basin became a favorable region to apply ANT techniques with the implantation of the FAPESP 2013/24214-6 Project (http://www.moho.iag.usp.br/about/projects/PCPB/), that deployed 38 stations through the region. ANT is based on the noise correlation between pairs of seismographic stations. The ambient noise is a random wave field produced by oceanic and atmospheric variations. From the group and phase velocity maps it was not possible to obtain a resolution of the influence of the sediment layer for the Pantanal Basin, indicating that it is much less thick compared to the neighboring basins, as well as the crustal thickness which does not exceed 35km. The inversion maps of sedimentary and crustal thickness indicated Moho depths of 1km and 32km respectively. The results also shown that TBL seem to separate thicker and thinner areas around the region.