Animation Based on Satellite Data Shows SoCal “Breathing” Water

Caltech News tagged with “astronomy + exoplanets + JPL + planetary_science”

Using an unprecedented number of satellite radar images, geophysicists at Caltech have tracked how the ground in Southern California rises and falls as groundwater is pumped in and out of aquifers beneath the surface.Their findings are presented in a study that tracks deformation of the earth’s surface over an 18-year period. The work can be used by water management districts to assess the precise shape and size of aquifers and the impact of the region’s water use on those aquifers. The work also reveals what could be a previously unmapped fault running across northeast Orange County.”What we see through the rising and falling of the ground surface is the elastic response of the land to regular changes in groundwater level,” says lead author Bryan Riel (MS ’14, PhD ’17), who was a graduate student in the lab of Caltech’s Mark Simons at the time of the research, and is now a signal analysis engineer at JPL, which is managed by Caltech for NASA. “Because we have data over a long period of time, we were also able to isolate long-term surface deformation signals, including subsidence of the land that seems to be caused by compaction of clay layers in response to background variations in groundwater withdrawal.” Riel and Simons were also able to see sharp features where water was not flowing, which can indicate boundaries of aquifers as well as faults.The study, which was published online on April 30 by the journal Water Resources Research, uses publicly available radar data captured between 1992 and 2011 by European Space Agency satellites. The satellite data was compiled into 881 radar interferograms—images created by bouncing radar signals off of the earth’s surface—to track nearly vertical ground motion down to the millimeter with a horizontal resolution of tens of meters, over an area that stretches from San Fernando, northwest of downtown Los Angeles, …

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