A UA hydrology professor says we can use lightning, earthquakes, storm events, barometric variations, river-stage variations, and other natural phenomena, as power sources to carry out CAT-scans of groundwater basins.
The paper, A view toward the future of subsurface characterization: CAT scanning groundwater basins, by Tian-Chyi Jim Yeh in UA Department of Hydrology and Water Resources and a bevy of co-authors was published today in AGU's Water Resources Research journal. [above: from Yeh, et al, 2008, WRR]
The goal is "high-resolution characterization, monitoring, and prediction" towards understanding and prediction of subsurface processes at basin scales.