A SIMULATION STUDY OF GEOMETRIC ANISOTROPY DETECTION METHODS

In this paper, we investigated the detection of geometric anisotropy (GA) using four directional variograms that produce four sets of parameters. Four angles and corresponding ranges, which are the parameters of the directional variogram models, were used for (cid:12)tting ellipse parameters to detect GA. The (cid:12)tted ellipse indicates the GA determined by the ratio between the semi-major and the semi-minor axes and the rotated angles of the semi-major axis. Another way of detecting GA is to use the likelihood of the data prediction process (the maximum likelihood method). We performed simulation experiments to compare these two methods for detecting GA in addition to a third method that assumes isotropy. Such simulation experiments generate various kinds of GA to evaluate the validity of the three methods. The results of the simulation study showed that, in the case of a small number of data or strong GA, our method provided good results. In contrast, the other two methods only occasionally produced good results.