1. 2011 IEEE International Geoscience and Remote Sensing Symposium FR2.T09.5 - GIS Techniques III Caldera Rims of Northeast Honshu Extracted from Gravity Anomalies and Aeromagnetic Data Oky Dicky Ardiansyah, PRIMA (Prima, O.D.A.) Faculty of Software & Information Science, Iwate Prefectural University 152-52 Sugo, Takizawa, Iwate 020-0193, JAPAN Takeyoshi, YOSHIDA (Yoshida, T.) Institute of Min., Pet. & Eco. Geol., Grad. School of Sciences, Tohoku Univ. 6-3 Aoba, Aramaki, Sendai 980-8578, JAPAN Takeshi, KUDO (Kudo, T.) Department of Natural Science and Mathematics, Chubu University 1200, Matsumoto-cho, Kasugai-shi, Aichi 487-8501, JAPAN
10. Research Aim To automatically extract the topographic rim of buried caldera (with diameters ranging from 5 to 30 km) from gravity anomalies and aeromagnetic data using “watershed delineation” in GIS. Lowest point (sink) Gravity anomalies Ex: Watershed delineated from a DEM
11. Data Gravity anomalies Aeromagnetic data (published by the Geological Survey of Japan, 2000, 2004) (published by the Geological Survey of Japan, 2005)
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13. Data filtering for gravity anomalies Eliminate noises using 2D FFT (Cut-off wavelength is empirically determined) Trend Fourier amplitude spectrum (log) Signal Noise km ← long Wavelength short -> Typical spectral distribution of gravity anomaly (Nozaki, 1997)
14. Watershed Delineation Delineating boundaries of concave (or convex) in gravity and aeromagnetic data is similar with that of watersheds from a digital elevation model (DEM) using hydrological modeling but without “depression-filling” process. A concave form in the data
15. Rim extraction with ArcGIS model builder Input data Reproject data Clip region of interest Calculate flow direction Calculate watershed Vectorize the boundary of watershed
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21. Conclusion In this study, we have extracted caldera rims of Northeast Honshu, Japan depending on their forms: concave and convex, from gravity anomalies and aeromagnetic data. Gravity anomalies seem to be superior on extracting caldera rims. However, there are some caldera rims that were extracted only from aeromagnetic data. Thank you for your attention
