This animation shows a cumulative view of earthquake activity for the whole world from 1980 through 1995. Each dot on the image represents the number of earthquakes with magnitude greater than 4.2 that have occurred in a 0.35 by 0.35 degree area of the globe since January 1, 1980. A yellow dot represents 1 or 2 earthquakes, an orange dot represents about 10 earthquakes, and a red dot represents 50 to 200 earthquakes. The background image, if present, shows the topography of the ocean floor. As the animation proceeds, the earthquakes clearly accumulate around the topographic features that represent the boundaries of the Earth's crustal plates. This animation is based on data from world-wide seismic networks and was obtained from the National Earthquake Center of the United States Geological Survey.
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 220.127.116.11.0