The modified Mercalli (MM) intensity scale is composed of 12 increasing levels of intensity that range from imperceptible shaking to catastrophic destruction and is designated by Roman numerals I through XII. Although qualitative in nature, it can provide a more concrete model for middle and high school students striving to understand the dynamics of earthquake behavior. Immediately after an earthquake, trained observers go into an earthquake-affected area and note the degree of physical destruction and record the observations of eye-witnesses. These observations and various degrees of destruction are evaluated according to their positions on the modified Mercalli intensity scale and plotted very carefully on a map of the affected area. The points of equal Mercalli intensity are then connected to from isoseismal lines (lines of equal seismic intensity). What commonly occurs is a relatively simple pattern of concentric "contours," with the greatest intensity at the epicenter of the earthquake and progressively lesser intensities at greater distance from the epicenter. Frequently, the pattern of isoseismal lines is elongated along the trace of the fault that caused the earthquake. This allows geologists to deduce the approximate position of the fault and locate it on the map, and is something students will do as part of this activity. Drawing contours should be familiar to students who have previous experience drawing contour maps. For students without previous experience, it is best for the teacher to demonstrate how the position of these lines is estimated from the data and how they can never cross. This activity is easily modified to meet the needs of the curriculum and students. It can be used for enrichment, as a supplement, or as a stand-alone activity that will help students to better understand the Mercalli scale. The activity also provides a more concrete explanation of the variation in the destruction students see via the media or that they have experienced firsthand in an earthquake. (Contains 7 figures.)