Magnitude and intensity are both related to the size of an earthquake, but they each measure different aspects. Magnitude, (which measures the energy released at the source of the earthquake rupture, is calculated using measurements from seismic instruments) is one single value. Seismic intensity, which is the measurement of the strength of shaking at a specific location determined from effects on people, human structures, and the natural environment, produces a range of shaking intensities in different locations. Thus, unlike earthquake magnitude, which is the same for all locations, the seismic intensity you feel depends on where you are. Intensity is mostly controlled by three factors: 1) magnitude (how big the earthquake was), 2) distance from the hypocenter (intensity varies from place to place), and 3) the local rock and soil conditions. Let's compare magnitude and intensity by using a light bulb as an analogy. The light bulb represents the location within the earth called the hypocenter where the earthquake begins. The magnitude, or size of an earthquake, is like the wattage of a light bulb. Just as the wattage represents the amount of power of the light bulb, the magnitude is related to the total amount of energy released by the earthquake source. The intensity, or shaking level, is like the amount of light from a light bulb at any spot in a room. A small light bulb in one area of a room will make that area bright with high intensity light but it will leave the distant areas of the room dim with low intensity light. So a given earthquake has only one magnitude but will produce different intensities of ground shaking as shown on the USGS did you feel it intensity Maps.