When the magnitude 9.0 Tohoku-Oki earthquake and resulting tsunami struck off the northeast coast of Japan on March 11, they caused widespread destruction and death. Using observations from a dense regional geodetic network (allowing measurements of earth movement to be gathered from GPS satellite data), globally distributed broadband seismographic networks, and open-ocean tsunami data, researchers have begun to construct numerous models that describe how the earth moved that day.

For many people, Global Positioning System (GPS) satellite technology is little more than a high-tech version of a traditional paper map. Used in automobile navigation systems and smart phones, GPS helps folks find their way around a new neighborhood or locate a nearby restaurant. But GPS is doing much, much more for researchers at the California Institute of Technology (Caltech): it's helping them find their way to a more complete understanding of Earth's interior structure. 

Caltech scientists and students are among a group of government and university researchers collecting seismic images of the Imperial and Coachella Valleys this week.

About 450 million years ago, Earth suffered the second-largest mass extinction in its history—the Late Ordovician mass extinction, during which more than 75 percent of marine species died. Exactly what caused this tremendous loss in biodiversity remains a mystery, but now a team led by researchers at Caltech has discovered new details supporting the idea that the mass extinction was linked to a cooling climate.