Produção Científica

**Artigo em Revista**

Source parameters and rupture velocity of small? 2.1 reservoir induced earthquakes.We calculate stress drop and rupture speed for ML â‰¤ 2.1 shallow reservoir induced earthquakes and ï¬nd them to be similar to those of large, natural earthquakes. Previous studies have suggested that hydrofractures, mining and reservoir-induced earthquakes have lower average stress drop than natural tectonic earthquakes. This difference might result from the different tectonic setting or the shallower hypocentral depths of induced earthquakes. Alternatively, difï¬culties in correcting for attenuation and site effects in earlier studies may lead to underestimation of stress drop. In addition, most studies assume the rupture velocity of small reservoir induced earthquakes to be the same as for the large earthquakes. We analyse a set of 101 ML â‰¤ 2.1 earthquakes induced by changing water level in the AcÂ¸u Reservoir, NE Brazil. The earthquakes are shallow, (depth <5 km) and the region has negligible natural seismicity. We use three different approaches to calculate the source parameters of the six largest (1.9 â‰¤ ML â‰¤ 2.1) earthquakes. We model the individual spectra to ï¬nd corner frequency, frequency-independent Q, and long period amplitude. We use collocated small earthquakes as empirical Greenâ€™s functions to calculate the spectral ratios, and determine the relative source time functions. Estimates of the source duration and corner frequency imply stress drops in the range of 26â€“179 MPa. These are similar to, or higher than tectonic earthquakes suggesting that the shallow hypocentral depth and the presence of water do not affect stress drop. We observe clear directivity for one of the earthquakes, and use the azimuthal variation in pulse width to estimate a rupture velocity of â‰¥0.6Î². |

**Artigo em Revista**

SS-traveltime parameters from PP and PS reflections.The SS-wave traveltimes can be derived from PP- and PS-wave data with the previously derived method. We have extended this method as follows. (1) The previous requirement that sources and receivers be located on a common acquisition surface is removed, which makes the method directly applicable to PS-waves recorded on the ocean bottom and PP-waves recorded at the ocean surface. (2) By using the concept and properties of surface-to-surface propagator matrices, the second-order traveltime derivatives of the SS-waves are obtained. In the same way as for the original method, the proposed extension is valid for arbitrary anisotropic media. The propagator matrix and geometric spreading of an SS-wave reflected at a given point on a target reflector are obtained explicitly from the propagators of the PP- and PS-waves reflected at the same point. These additional parameters provided by the extended method can be used for a partial reconstruction of the SS-wave amplitude as well as for tomographic estimation of the elastic velocity model. A full simulation of the SS-wave, which includes reflection and transmission coefficients, cannot be obtained directly from recorded PP- and PS-wave amplitudes. |

**Artigo em Revista**

A new stabilized least-squares imaging condition.The classical deconvolution imaging condition consists of dividing the upgoing wave field by the downgoing wave field and summing over all frequencies and sources. The least-squares imaging condition consists of summing the cross-correlation of the upgoing and downgoing wave fields over all frequencies and sources, and dividing the result by the total energy of the downgoing wave field. This procedure is more stable than using the classical imaging condition, but it still requires stabilization in zones where the energy of the downgoing wave field is small. To stabilize the least-squares imaging condition, the energy of the downgoing wave field is replaced by its average value computed in a horizontal plane in poorly illuminated regions. Applications to the Marmousi and Sigsbee2A data sets show that the stabilized least-squares imaging condition produces better images than the least-squares and cross-correlation imaging conditions. |

**Material Didático**

Carlos Alberto Dias - A saga da GeofÃsica Aplicada e da Engenharia de E&P do PetrÃ³leo no Brasil.Fernando S. de Moraes (Org.); Lima, O. A. L. de (Org.); JessÃ© C. Costa (Org.); Francisco Nepomuceno Filho (Org.). 1. ed. Salvador: Editora da Universidade Federal da Bahia, 2009. v. 1. 265 p. |

**Material Didático**

CÃ¡lculo NumÃ©rico.Marcelo Gomes Pereira ; Roberto Hugo Bielschowsky. 1. ed. Natal: SEDIS - EDUFRN, 2009. v. 01. 300 p. |

**Material Didático**

Conceitos de GeofÃsica.A.F. do Nascimento, F.H.R. Bezerra, W.E. Medeiros, 2010. Natal: Editora EDUFRN. (Livro texto para a disciplina Conceitos de GeofÃsica do Curso de FÃsica Ã distancia da UFRN.) |

**Apresentação**

The use of discrete wavelet transform in road loads signals.ANDRADE, G. S.; DUARTE, A. A.; SCHNITMAN, L.. In: CONGRESSO SAE BRASIL, 2009, SÃ£o Paulo. Anais do Congresso SAE Brasil 2009, 2009. |

**Apresentação**

AplicaÃ§Ã£o de Redes Neurais Artificiais no Reconhecimento de PadrÃµes de Cartas DinamomÃ©tricas de Sistemas de Bombeio MecÃ¢nico de PetrÃ³leo.BEZERRA, Marco A.D.; BARRETO FILHO, Manoel de A.; SCHNITMAN, L.. In: IX SimpÃ³sio Brasileiro de AutomaÃ§Ã£o Inteligente, 2009, BrasÃlia. Anais do IX SimpÃ³sio Brasileiro de AutomaÃ§Ã£o Inteligente, 2009. v. 9. |

**Apresentação**

Alternative concepts for the high precision bearings in torque standard machines.BITENCOURT, AntÃ´nio Carlos Peixoto; THESKA, R.; Wagner, A.; LEPIKSON, H. A.; WEINGAERTNER, W.. In: 10th Int Conf of the European Society for Precision Engineering & Nanotechnology, 2010, Delft. Proceedings of 10th Int Conf of the European Society for Precision Engineering & Nanotechnology. Cranfield, England : Euspen - European Society for Precision Engineering & Nanotechnology, 2010. v. 1. p. 474-477. |

**Apresentação**

UM SISTEMA CAM PARÃ MÃQUINAS DE PROTOTIPAGEM RÃPIDA DE BAIXO CUSTO.MARTINS, S.R.M.; LEPIKSON, H. A.; COSTA, B.L.S.. In: VI CONEM - Congresso Nacional de Engenharia MecÃ¢nica, 2010, Campina Grande, PB. Anais do VI CONEM - Congresso Nacional de Engenharia MecÃ¢nica. Rio de Janeiro, RJ : ABCM - AssociaÃ§Ã£o Brasileira de CiÃªncias e Engenharia MecÃ¢nica, 2010. v. 1. p. 1-9. |

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