Figure 6. The solid-line curve is the spatial attenuation of intensity
Equation (1) based on the least-squares fit to the 02:15 A.M. December
16, 1811, intensity data illustrated in Figure 5a.
The other two curves are based on the work of Howell and
Schultz (Equation 19, pg. 660, 1975), Gupta and Nuttli
(1976), and the assumption that the epicentral intensity of
the 02:15 A.M. December 16, 1811, event is XI MM as suggested
by Nuttli (1979).