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Modified Mercalli Scale
| MM I | MM 1 | Not felt | People do not feel any Earth movement. |
| MM II | MM 2 | Weak | A few people might notice movement if they are at rest and/or on the upper floors of tall buildings. |
| MM III | MM 3 | Weak | Many people indoors feel movement. Hanging objects swing back and forth. People outdoors might not realize that an earthquake is occurring. |
| MM IV | MM 4 | Light | Most people indoors feel movement. Hanging objects swing. Dishes, windows, and doors rattle. The earthquake feels like a heavy truck hitting the walls. A few people outdoors may feel movement. Parked cars rocked. |
| MM V | MM 5 | Moderate | Almost everyone feels movement. Sleeping people are awakened. Doors swing open or close. Dishes are broken. Pictures on the wall move. Small objects move or are turned over. Trees might shake. Liquids might spill out of open containers. |
| MM VI | MM 6 | Strong | Everyone feels movement. People have trouble walking. Objects fall from shelves. Pictures fall off walls. Furniture moves. Plaster in walls might crack. Trees and bushes shake. Damage is slight in poorly built buildings. No structural damage. |
| MM VII | MM 7 | Very strong | People have difficulty standing. Drivers feel their cars shake. Some furniture breaks. Loose bricks fall from buildings. Damage is slight to moderate in well-built buildings, considerable in poorly-built buildings. |
| MM VIII | MM 8 | Severe | Drivers have trouble steering. Houses that are not bolted down might shift on their foundations. Tall structures such as towers and chimneys might twist and fall. Well-built buildings suffer moderate damage. Poorly-built structures suffer severe damage. Tree branches break. Hillsides might crack if the ground is wet. Water level in wells might change. |
| MM IX | MM 9 | Violent | Well-built buildings suffer considerable damage. Houses that are not bolted down move off their foundations. Some underground pipes are broken. The ground cracks. Reservoirs suffer serious damage. |
| MM X | MM 10 | Extreme | Most buildings and their foundations are destroyed. Some bridges are destroyed. Dams are seriously damaged. Large landslides occur. Water is thrown on the banks of canals, rivers, lakes. The ground cracks in large areas. Railroad tracks are bent slightly. |
| MM XI | MM 11 | Extreme | Most buildings collapse. Some bridges are destroyed. Large cracks appear in the ground. Underground pipelines are destroyed. Railroad tracks are badly bent. |
| MM XII | MM 12 | Catastrophic | Almost everything is destroyed. Objects are thrown into the air. The ground moves in waves or ripples. Large amounts of rock may move. |
An example of a proper response is: “(your-call-sign), Mike-Mike-4, Tres Pinos”
The Modified Mercalli, or Mike-Mike scale is used to standardize and make more efficient the reporting of earthquake damage. Instead of reporting damage by using general descriptions like “major” or “minor” or “heavy”, a Mike-Mike value is reported. This value is quick and simple to communicate over the air and equates to a standard level of damage as defined in the scale below.