FIG. 11. A/T versus epicentral distance of the vertical component of Rayleigh-wave motion for the earthquakes of November 9, 1968 and December 16, 1811. The Roman numerals indicate MM intensity values. The curve for the November 9, 1968 earthquake is the attenuation curve for 3-sec period waves (Figure 6). The short horizontal bars are drawn to cross this curve at the points which correspond to intensities VII to IV. The +'s are plotted at the distance at which the corresponding intensities were observed to the east for the December 16, 1811 earthquake. They are fit by a theoretical (solid-line) attenuation curve with the same coefficient of anelastic attenuation, y, as that used for the November 9, 1968 earthquake. The O's are plotted at the distances at which the corresponding intensities were observed in the north-south directions (average distances) for the December 16, 1811 earthquake. They are fit by a theoretical attenuation curve (dashed line) for which y is greater than for the other curves in the figure.