Seminário LabSis de 04/09/2014

    Quinta-feira, dia 04/09, às 15:30 h, no auditório do Módulo REUNI do Departamento de Geofísica, acontece o segundo seminário do LabSis, do ciclo de 2014. O palestrante será o doutorando Esteban Poveda. 

Título: Crustal thickness estimation beneath the Northern Andes using the receiver function method

Resumo:

We calculated receiver functions under the Northwestern Andes and adjacent areas, to deduce crustal thickness. For this purpose, we use data from the broadband network of Colombia, which has been working since 2008; presently the network consists of 29 stations, 10 of which have been installed between 2012 and 2014, and are operated by the Colombian Geological Survey. Recent stations were installed to improve the epicentral locations in the SGC where there was a high azimuthal gap. With the receiver function calculation, we were able to map crustal thickness and Vp/Vs ratio in regions of the Northwestern Andean system where there were no previous estimations. We also collected information of Moho depth from previous studies and neighboring regions to present a new map of interpolated crustal thickness of the Northern Andes. Our results included a wide range of crustal thicknesses, with values of around 14 km beneath the Malpelo Island on the Pacific ocean, 20 to 30 km at the coastal Pacific and Caribbean plains of Colombia, 25 to 35 km beneath the eastern plains and foothills, 34 to 40 km beneath the Western Cordillera, 40 to 45 km at the Magdalena River intermountain valley, 53 to 58 km in the northern Central Cordillera, and reaching almost 60 km beneath some of the volcanoes of the southern cordilleran system of Colombia and the Plateau of the Eastern Cordillera. The Vp/Vs ratio was obtained using a combination of Wadati diagrams and a H-k (crustal thickness – Vp/Vs) stacking technique, which gave a bulk value for most of the crust under each station. In general, high values of Vp/Vs are associated to regions of high crustal thickness, and volcanic and high temperature gradient areas. The low Vp/Vs values are located in the intermountain valleys, regions of relatively low crustal thickness and areas where oceanic material has been accreted to the continent. The continuation of this work will consist of the collection of Love and Rayleigh surface wave dispersion observations, in order to combine the surface wave data and receiver functions to perform a joint inversion to obtain a more precise crust-mantle velocity structure.

Palavras-chave: Crustal thickness, receiver functions, H-k stacking and joint inversion.

Fonte: LabSis/UFRN

Esteban Poveda, Jordi Julià, Rodrigo Pessoa, Joaquim Ferreira