Sismicidade em Pedra Preta-RN no período de 2013-2014

Abstract

The seismic activity in Preta Pedra-RN began in December 2010. Before that, there was no record earthquakes in this area, located in the Brazilian Northeast, where is recorded the largest intraplate seismicity of Brazil. During 2013 and early 2014, the seismographic network Pedra Preta registered 273 local earthquakes in three or more stations. The entire data set of this work was analyzed in the COMPASS software. By Wadati diagram were selected 50 events with the best readings from the arrival times of P and S waves. With the help of HYPO71 program, was determined the velocity model (Vp / Vs = 1,72 and Vp = 5.90 km/s) and calculated the hypocenters. For the determination of the composed focal mechanism, these was a new selection of earthquakes obeying more stringent criteria for the hypocenters (Gap <180, RMS ≤ 0.01 s, Number of observations ≥ 10, ERH <0.1 km, ERZ <0, 1 Km), selecting 24 events. The hypocenters of earthquakes show that the seismogenic fault is about 3 km long, with earthquakes between 2.3 to 5.8 kilometers deep. The parameters of seimogenic fault were obtained by combining the method of least squares and FPFIT program (strike = 254°, dip = 67° and the rake = -66°), indicating a normal fault. The epicenters and focal mechanism were used to verify whether there was possible correlations with geological features mapped in the study area. The conclusion is that there are no mapped geological features that may be directly related to the seismic activity studied.