You will also ensure that your area has been represented in the compilation of the shaking map. This is a two-way street. Not only will you add valuable information on the extent of ground shaking and damage, but in the process we hope you will learn more about how other communities fared and gain a greater understanding of the effects of earthquakes. There are two different ways to describe the size of an earthquake. The second way of describing earthquake size is to measure earthquake effects.
Intensity is a qualitative measure of the strength of ground shaking at a particular site.
Each earthquake which is large enough to be felt will have a range of intensities. Roman numerals are used to describe intensities to distinguish them from magnitudes. For example, the magnitude of the Northridge earthquake was 6.7. We consider all the filled-out questionnaires from a given ZIP code and assign a single intensity to the ZIP code. The decimal intensity values computed by the algorithm of Dengler and Dewey have been rounded off to integers for the Community Internet Intensity Map and represented by Roman Numerals.