Aplicação do método de função do receptor para determinação da estrutura da crosta e manto superior sob a Região Sul do Brasil

Abstract

Currently, most of the seismological studies carried out in Brazil are concentrated in the Southeast and Northeast regions of the country. However, the southern portion of the Paraná and Mantiqueira provinces, as well as the transition between these domains have not yet been adequately sampled by seismographic stations, so that their deep structure (crust and upper mantle) is not known with sufficient resolution. In this project, we were used data from three permanent stations, belonging to the Brazilian Seismographic Network (RSBR) located in the state of Rio Grande do Sul, in the towns of Canela, Caçapava do Sul and Pedras Altas / Pelotas, named CNLB, CPSB and PLTB, respectively. The objective of the work is to use the Receiver Function (FR) method, which has been widely used in research studies of the crust and upper mantle, in order to obtain a model of the structure of the crust and the upper mantle, in terms of the ratio between The seismic velocities (Vp / Vs) and crustal thickness, below the seismographic stations located in the South-Rio-Grandense Shield and the Paraná Basin. This method uses P-type flat-wave fronts from distant earthquakes, which, when incident on a discontinuity, such as Mohorovicic discontinuity, below the seismographic station with an angle close to vertical, converts to S wave (Ps) and wave reflections S (multiple, predominant in radial). These waves, when they reach the stations, also bring information about the source and the course in the mantle. Applying the deconvolution in the records of the radial component by the vertical component, it is possible to remove these effects, obtaining in the form of a time series, the equivalent response to the internal structure of the Earth under the seismographic station, denominated FR. From the analysis of a set of traces of the Receiver Function, CPSB - crustal thickness of 35.0 ± 0.2 km and Vp / Vs ratio = 1.78 ± 0.00; CNLB - crustal thickness of 40 ± 0.4 km and ratio Vp / Vs = 1.75 ± 0.00; PLTB - crustal thickness 36 ± 0.1 km and Vp / Vs ratio = 1.81 ± 0.00. The receiver function method presented excellent results in order to contribute with some geological information under the CNLB, PLTB and CPSB stations under study. keywords: Receptor function, seismographic stations, discontinuity.