When LANDSAT cameras returned images of the Earth from space several decades ago, it changed our perspective forever. Faults such as the San Andreas were viewed in unprecedented clarity, and other, previously unknown earthquake-producing structures were also revealed. The Geodynamics Program at NASA was developed to take advantage of the new space platforms as a means to learn about the Earth, including plate tectonics, mineral resources, and an understanding of earthquakes. These activities are now coordinated in a program called Earth Systems Enterprise, managed by the Jet Propulsion Lab in Pasadena.
In December 1999, NASA launched a satellite named Terra, the Earth Observing System, to map the Earth in real time, tracking changes on the Earth’s surface observed from space. In February 2000, the space shuttle Endeavour conducted an eleven-day radar mapping survey of the Earth, resulting in much more accurate topographic maps than had been available previously.
The greatest impact NASA has had on earthquake research has been in the measurement of crustal strain from space (described in Chapter 3). This includes the measurement of the relative motion of radio telescopes based on measuring signals from quasars in outer space, the measurement of strain through the Global Positioning System based on signals from NAVSTAR satellites, and the direct measurement of displacement during an earthquake based on radar interferometry. Much of this work is coordinated through NASA’s Jet Propulsion Lab. Radar interferometry revealed an area of rising crust west of the South Sister volcano in Oregon, a suggestion that magma was moving upward beneath the Earth’s surface. Three satellites provide radar data, two from Europe and one from Canada.