Resumo

DAVILA-HERNANDEZ, Norma; LIRA, Jorge; CAPRA-PEDOL, Lucia  e  ZUCCA, Francesco. A normalized difference lahar index based on Terra/Aster and Spot 5 images: an application at Colima Volcano, Mexico. Rev. mex. cienc. geol [online]. 2011, vol.28, n.3, pp.630-644. ISSN 2007-2902.

For the evaluation of recent lahar deposits, we propose a Normalized Difference Lahar Index (NDLI) based on the analysis of eigenvectors of Principal Components Analysis (PCA) applied to Terra/Aster and Spot 5 multispectral images of the Colima Volcano. As a result, the normalization of bands 3 and 4 of both sensors produces the best results for the spectral enhancement of lahar deposits with respect to the rest of the components in the image. Such normalization is the basis for the NDLI. For the validation of results in this case of study, fieldwork was carried out based on ground control points (GCP) on the hillsides of Colima Volcano. Likewise, to corroborate the validity of the NDLI, we performed enhancements and segmentations of lahar deposits using a Variant of Principal Component Analysis (VPCA) and a region growth algorithm. These enhancements and segmentations were compared with results from the NDLI. The application of the NDLI allows the identification of new deposit units and new alluvial fan forms from recurrent lahar deposits, principally on Montegrande and San Antonio ravines on the south flank of the volcano. The application of remote sensing techniques, as the introduction of the NDLI, is a useful tool for the identification of lahar deposits associated to recent volcanic activity.

Palavras-chave : lahar deposits; spectral enhancement; lahar segmentation; variant of Principal Components Analysis; Terra/Aster image; Spot 5 image.

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