Figure 2.5



Figure 2.5A Figure 2.5B Figure 2.5C

Computed geotherms for the Grenville region, (A) using parameters of Table2.1. Five curves are shown: the absolute Maximum (MAX) and Minimum (MIN) geotherrns; the Average (Av) geotherm which represent the average value of all geotherms at a given depth; and the MIN90% and MAX90% which enclose 90% of all geotherms. Ninety-nine percent of all earthquakes occur above D99% . (B) Temperature variations due to one parameter while others are kept at their average values of Table 2.1. Surface heat flow is the most important factor, while all others constrain geotherm fluctuations within 50C when the average heat flow is used. (C) Comparisons of MIN90%, AV, and MAX90% geotherms with the geotherms of Chapman (1986) for a surface heat flow of 40 mW/m2 (Ch40) and 50 mW/m2 (Ch50). Both fall within the present 90% confidence margin.