Prediction of Occurrence of Discrete Events - Geomathematics: Theoretical Foundations, Applications and Future Developments - page 147

Anticline Binary Pattern
Mapid : fbM2

Legend

less favourable distance
more favourable (c1.25 km)
20 KM

Weight for feature present w+ = 0.5452

Weight for feature absent w− = −0.7735

Fig. 5.5 Binary pattern for proximity to axial traces of Acadian anticlines (Source: Bonham-
Carter et al. 1988 , Fig. 3a)

are known on these two formations in the study area. Bonham-Carter et al. ( 1990 )
added a ternary map pattern for biogeochemical measurements of gold in balsam fir
to the six map patterns used in earlier applications. Inspection of the standard
deviations of the contrasts in Table 5.1 shows that spatial correlation of the
68 gold deposits with NW lineaments and granite contact is probably not statisti-
cally significant because the ratio of the contrast C and its standard deviation ( C )is

less than 1.96 representing the 95 % confidence limit based on a two-sided z -test
( cf . Sect. 2.3.3 ). Figures 5.7 and 5.9 show posterior probability maps obtained
without and with use of the ternary pattern for gold in balsam fir that is shown in
Fig. 5.8 . The effect of adding the Au in balsam fir data is quite pronounced as shown
by comparing the two posterior probability maps (Fig. 5.9 versus Fig. 5.7 ).
Table 5.2 illustrates how the pattern shown in Fig. 5.8 was selected. Weights,
contrasts and their standard deviations were calculated for a series of different Au
levels. Although the maximum value of W + occurs by thresholding at the 90th
percentile, the maximum contrast C occurs for the 80th percentile. At this level,
24 out of 68 gold deposits fall within the balsam fir Au anomaly, which occupies
435 km 2 out of a total of 2,591 km 2 .
The Kolmogorov-Smirnov test (Fig. 5.10 ) can be used to test the hypothesis of
conditional independence of the seven map layers used for Fig. 5.9 . This hypothesis

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