Banca de DEFESA: HUGO ESTEBAN POVEDA NUÑEZ
Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.DISCENTE : HUGO ESTEBAN POVEDA NUÑEZ
DATA : 29/08/2018
HORA: 09:00
LOCAL: Auditório do Departamento de Geofísica
TÍTULO:
Crustal and upper mantle shear-wave velocity structure and radial anisotropy beneath the Colombian Andes inferred from ambient noise and surface wave tomography
PALAVRAS-CHAVES:
Ambient noise tomography; Surface wave tomography; Radial anisotropy; Subduction-related volcanism; South America.
PÁGINAS: 250
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Geociências
RESUMO:
This thesis aims at investigating how subduction-related processes in the Colombian Andes deform and alter the composition of the overriding plate. To that purpose, the S-wave velocity structure and radial anisotropy within the crust and upper mantle have been investigated. A total of 1,300 empirical Green’s functions from ambient noise cross-correlations and 11,000 fundamental-mode, surface-wave trains from local and regional earthquake sources have been analyzed. Phase- and group-velocity curves for Rayleigh and Love waves were measured in the 7-150 s period range from the combined dataset, and tomographically inverted to produce maps of phase- and group-velocity variation in a 0.5 ˚ x 0.5˚grid for ambient noise and 1.0˚ x 1.0˚ for surface waves. VSV and VSH velocity-depth profiles were then constructed from the joint inversion of local group and phase dispersion curves at each node in the tomographic grid down to 140 km depth. The S-velocity models reveal zones of slow velocity at 25-35 km depth under regions of both active and inactive volcanism, suggesting the presence of melts that carry the signature of segmented subduction into the overriding plate. The regions of slow crustal S-velocity display negative radial anisotropy (VSH < VSV) under active volcanoes, suggesting the presence of sub-vertical magmatic dykes feeding the volcanics, and positive radial anisotropy (VSH > VSV) under inactive volcanic regions, consistent with magma storage along flat-lying sills. At 40 km depth, slow velocities under the Central and Eastern cordilleras display positive radial anisotropy (up to 15%), which is interpreted as storage of subduction-related magmas in the lower crust. Slow S-velocities with positive radial anisotropy are observed in the Lower Magdalena Basin at all crustal levels, consistent with a combination of alternating fast and slow velocities within the sedimentary package, extensional stresses, sub-horizontal shear, and/or sub-lithospheric melts from a fractured Caribbean flat slab. Negative radial anisotropy is also observed under Lower Magdalena Basin at upper mantle levels, coinciding with the location of the Caribbean flat slab.
MEMBROS DA BANCA:
Interno - 350640 - FRANCISCO HILARIO REGO BEZERRA
Externo à Instituição - GERMÁN PRIETO GÓMES
Presidente - 1863578 - JORDI JULIA CASAS
Externo à Instituição - MARCELO SOUSA DE ASSUMPÇÃO - USP
Interno - 349684 - WALTER EUGENIO DE MEDEIROS