Principle and geomorphological applicability of summit level and base level technique using Aster Gdem satellite-derived data and the original software Baz/Principio e aplicabilidade das tecnicas de seppomen e sekkokumen para analises geomorfologicas com base nos dados de satelites do Aster Gdem e o software original Baz

This article presents principle and geomorphological applicability of summit level technique using Aster Gdem satellite-derived topographic data. Summit level corresponds to the virtual topographic surface constituted by local highest points, such as peaks and plateau tops, and reconstitutes palaeo-geomorphology before the drainage erosion. Summit level map is efficient for reconstitution of palaeo-surfaces and detection of active tectonic movement. Base level is the virtual surface composed of local lowest points, as valley bottoms. The difference between summit level and base level is called relief amount. These virtual maps are constructed by the original software Baz. The macro concavity index, MCI, is calculated from summit level and relief amount maps. The volume-normalised three-dimensional concavity index, TCI, is calculated from hypsometric diagram. The massifs with high erosive resistance tend to have convex general form and low MCI and TCI. Those with low resistance have concave form and high MCI and TCI. The diagram of TCI vs. MCI permits to distinguish erosive characteristics of massifs according to their constituent rocks. The base level map for ocean bottom detects the basement tectonic uplift which occurred before the formation of the volcanic seamounts. Keywords: summit level, base level, morphological analyses, palaeo-surface, erosive resistance, active fault. Este artigo apresenta o principio e a aplicabilidade geomorfologica da tecnica de seppomen e sekkokumen utilizando-se os dados topograficos de satelite do Aster Gdem. O seppomen corresponde a superficie topografica virtual constituida por pontos culminantes locais, tais como picos e topos de platos, e reconstitui a paleogeomorfologia antes da erosao por drenagens. O mapa de seppomen e eficiente para reconstituicao de paleossuperficies e deteccao de movimentos tectonicos ativos. O sekkokumen e a superficie virtual composta de pontos locais mais baixos, como fundo de vales. A diferenca entre seppomen e sekkokumen e denominada kifukuryo. Esses mapas virtuais sao elaborados pelo software original Baz. O indice de macro concavidade de macico, MCI, e calculado a partir dos mapas de seppomen e kifukuryo. O parametro de convexidade tridimensional normalizado por volume, TCI, e calculado por diagrama hipsometrico. Os macicos com alta resistencia erosiva tendem a ter forma geral convexa e altos MCI e TCI. Aqueles com baixa resistencia erosiva possuem forma concava e baixos MCI e TCI. O diagra