Journey to the centre of the Earth

probably the most ambitious seismological project ever conducted... USArray ... to run what amounts to an ultrasound scan over the 48 contiguous states of the US. Through the seismic shudders and murmurs that rack Earth's innards, it will build up an unprecedented 3D picture of what lies beneath North America. ... 400 transportable seismometers - will sweep all the way from the Pacific to the Atlantic. Having started off in California in 2004, it is now just east of the Rockies, stretching from Montana's border with Canada down past El Paso on the Texas-Mexico border. By 2013, it should have reached the north-east coast, and its mission end. ... "It is our version of the Hubble Space Telescope. With it, we'll be able to view Earth in a fundamentally different way..."