Simple three-dimensional display method for cross sections and columnar sections

NAKAZAWA T., NONOGAKI S., MIYACHI Y.

Eto C., Ishihara Y., Tanabe S., Kimura K., Nakayama T.

東京低地の地下には,最終氷期最盛期までに形成された開析谷とそれらを充填する沖積層が分布している.本研究では,東京低地北部のボーリング柱状図を用いて,沖積層のN値と岩相の3次元分布モデルの構築方法を検討し,構築したモデルの分布から,堆積システムを特徴付ける堆積物の空間的な分布を明らかにした.3次元分布モデルは,不規則に分布するボーリング柱状図の情報を2次元平面上で補間し,補間により作成された等間隔なデータセットを深度方向に積み重ねることで構築した.N値と岩相の3次元分布モデルは,蛇行河川システムの河川チャネル堆積物と氾濫原堆積物,砂嘴堆積物,海進期の砂州堆積物といった堆積体の分布を示している.

DOUGLAS D.H., PEUCKER T.K.

All digitizing methods, as a general rule, record lines with far more data than is necessary for accurate graphic reproduction or for computer analysis. Two algorithms to reduce the number of points required to represent the line and, if desired, produce caricatures, are presented and compared with the most promising methods so far suggested. Line reduction will form a major part of automated generalization. Regle generale, les methodes numeriques enregistrent des lignes avec beaucoup plus de donnees qu'il n'est necessaire a la reproduction graphique precise ou a la recherche par ordinateur. L'auteur presente deux algorithmes pour reduire le nombre de points necessaires pour representer la ligne et produire des caricatures si desire, et les compare aux methodes les plus prometteuses suggerees jusqu'ici. La reduction de la ligne constituera une partie importante de la generalisation automatique.

Walton G.G.

The three‐dimensional seismic method is a different way of gathering and presenting seismic data. Instead of showing the subsurface beneath a profile line, 3-D displays give an, areal picture from the shallowest reflector to the deepest one that can be found seismically. Data are collected in the field with cross‐spreads that provide over 2000 evenly spaced depth points on each reflecting interface. Several variations of the cross‐spread technique give the same subsurface coverage while providing flexibility in data gathering. Because of the dense coverage, the method is best suited for problems requiring great detail, such as production problems. The usual presentation of 3-D data is a visual, moving display of emerging wavefronts covering four sq mi of surface. From this dynamic display, average velocity to each reflector and the dip direction and magnitude can be computed. The method has proved especially useful for the recognition of faults and determination of fault directions.