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Emmanuel G. Ramos
Philippine Institute of Volcanology and Seismology





Digital processing and analysis of topographic data reveal details on the structures of Taal Volcano Island. The principles in spectral analysis were used to process the digital topographic data of Taal. The position and form of the various volcanic units were recognized through the deconvolution of the digital elevation model into wavelength components. Similar to the concept of spectral analysis in geophysics, the geomorphic filters used on the digital elevation model allow the visual identification of volcanic landforms. In many cases, the existence of nested cones and craters appear in filtered terrain maps while in some parts of the island, buried craters are revealed. The sequence in the development of the main crater through a series of explosions that occurred in 1911 can also be reconstructed, even if the processing was done on two data sources with different levels of detail. One is a 1:10,000 scale topographic map, and the other from a 1988 bathymetric map. Other features revealed by the geomorphic filtering procedure are faults and some subsidence-related fissures formed early during the 1965 eruption sequence, despite these being covered by tephra from subsequent eruptive events. The result of the digital analysis of topographic data is a refined geologic map of Taal Volcano.




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