- Earthquake Intensity Of the two ways to measure earthquake size, magnitude based on instrumental readings and intensity based on qualitative effects of earthquakes, only intensity can be applied to pre-instrumental earthquakes. The 1931 Modified Mercalli scale used in the United States assigns a Roman numeral in the range I - XII to each earthquake effect. The methodology is simple. At each ...www.eas.slu.edu/Earthquake_Center/mercalli.html
- Article from The National Geophysical Data Center. Although the history of the development of earthquake intensity scales is long and interesting, only a brief summary will be presented here.www.ngdc.noaa.gov/seg/hazard/intintro.shtml