Defense Advanced Research Projects Agency (DARPA) gave the ok to Failure Analysis to build the Defense Underground Mapping Satellite Tracking and Ranging (DUMSTR) system. The company proposed $100,000,000.00/year proposal to the National Reconnaissance Office (NRO) in February, 2008. The project is a a low-earth-orbiting, satellite-based, underground mapping matrix that will use existing Air Force satellite technology from the Defense Mapping Satellite Program (DMSP) and the Global Positioning System (GPS). The technology will allow the mapping of underground civil and military facilities around the world and "provide geological science information for plate tectonics, underground volcano structure and growth of lava chambers promising to increase the likelihood of future earthquake prediction capability."
SatNews.com
More seriously, I assume this uses some kind of Ground Penetrating Radar? There are hints that they might be trying to map gravitational potential, but I don't think that would work. Satellite-measured gravitational potentials have proved useful in plate tectonic studies, but from LEO do not have the accuracy to find underground facilities and magma chambers.
I also think they're overplaying the earthquake prediction. Volcanoes produce few earthquakes of significant size. And (unlike conventional double couple earthquakes) they are already predictable to an extent.
Old city walls under dry sand in the ar-Rub al-Hali? Yes.
A facility under moist soil or rock?
Not.
Gravimetry and surface change detection, comparing year-over-year changes and using them to guide visual changes at the surface nearby?
Hmmm, maybe there's something there...
It all seems too far fetched to me.
I think Archie was spot on regarding GPR, also, that technology has short range, maybe 10's of meters, but not hundreds, much less from orbit. For those not acquainted, GPR uses frequencies in the VHF spectrum and are low power transmitters, also, they only work when coupled to the ground. So, it is definitely not GPR.
As for gravimetry, I've seen it work for detecting underground "facilities" only when on is standing right on top of it. Grav looses too much resolution when you get far from the source.