Adding Up the Hazards

As an addendum to the core tectonic activity map, the Goddard team also made detailed global maps of earthquakes and active volcanoes — the two hazards that accompany tectonic activity. The earthquake data were retrieved from the National Geophysical Data Center and included the epicenters of the more than 200,000 earthquakes with magnitude over 3.5 that occurred between 1963 and 1998. The volcanic data, on the other hand, were taken from the Smithsonian Global Volcanism Program and showed the location of roughly 1,200 volcanic eruptions that are known to have taken place over the past 10,000 years (Lowman et al., 1999). Older volcanoes were added from other maps and satellite photos.

The Goddard team integrated all of these data and mapped each earthquake epicenter and volcanic center on the same base map they used to show tectonic activity. Most of the earthquakes and volcanoes are along or near plate boundaries. However, many can be found in unexpected areas. "Rarely do we think of active volcanoes existing in central China," Yates pointed out.

The final map Lowman and his team pieced together displays the movement of the Earth’s plates. Space geodesy stations all over the globe make precise measurements of how far the plates move each year. The movements range from next to nothing in Africa to more than 7 centimeters a year in areas such as the Pacific Basin. The Hawaiian islands, for example, are moving toward Asia at more than 8 centimeters a year. The Goddard researchers mapped these stations’ readings by indicating relative velocity and direction of crustal motion.

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Above: The Goddard geologists mapped earthquakes around the world from 1963 - 1998. Thousands occurred in the United States during that time.