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Where does seismic data come from? The data used to plot the locations and sizes of earthquakes in this edition of Earthrium was made available by the United States Geological Survey (USGS). The USGS is a governmental organization established in 1879, and was initially involved in researching mineral resources. These days is undertakes scientific surveys of natural resources such as water, organisms, energy, and geological features, and conducts research into natural disasters. The astronauts who landed on the Moon in 1969 as part of the Apollo program are said to have undergone geological training at the USGS. Seismic research is conducted at the USGS National Earthquake Information Center (NEIC), which is constantly releasing preliminary data on earthquakes as they occur. The information plotted on the globe at left is based on this NEIC data. If you click "Earthquakes in the last week," the locations and sizes of earthquakes that have occurred over the last seven days will be displayed. The center of each circle is the earthquake's epicenter, while the size of the circle indicates the earthquake's magnitude on the Richter scale. Quakes with a magnitude of 6 (M6) or greater are shown in red. The sizes of the circles are proportional to the magnitude by a power of two, although this does not accurately reflect the size of the quakes. In real life, an increase in a single magnitude represents an increase in the size of an earthquake by a factor of 32. So an M7 earthquake, for example, has 32 times more energy than an M6 earthquake, and around 1000 times (32 x 32) more than an M5 quake. The earthquake off the coast of the island of Sumatra was M9, a massive tremor equivalent to some one million M5 quakes. Click on the link below to display a list of quakes that have occurred over the last week (M2.5 or greater for the U.S. and surrounding area, and M4 or greater for the rest of the world). →List of earthquakes over the last week (NEIC) Click on "Earthquakes in 2005" to display the locations of M4 or greater quakes that occurred between January 1 and December 31, 2005. Tremors with epicenters 100 km or deeper are shown in red. You might notice that these quakes tend to be located inside the boundaries of tectonic plates. This is because most quakes with deep epicenters are caused by one plate moving under another. During 2005, there were nearly 16,000 tremors with a magnitude of 4 or greater (apologies for the length of time it takes for all the data to load). Looking at the results, it appears that the Earth is literally covered with earthquakes. It would certainly seem that the description "a seismic planet" is no exaggeration. Anyone may use this database, so feel free to access it any time. →Earthquake database search

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