Seismic Noise Tracks Water Levels in Underground Aquifers

A recent study that used seismic noise to measure the size and the water levels in underground aquifers in California. The technique could even be used to track whether and how aquifers rebound following precipitation, and understand geological changes that might occur as water is pumped out. 
 (Image: via   pixabay  /  CC0 1.0)
A recent study that used seismic noise to measure the size and the water levels in underground aquifers in California. The technique could even be used to track whether and how aquifers rebound following precipitation, and understand geological changes that might occur as water is pumped out. (Image: via pixabay / CC0 1.0)

Seismic noise — the low-level vibrations caused by everything from subway trains to waves crashing on the beach — is most often something seismologists work to avoid. They factor it out of models and create algorithms aimed at eliminating it so they can identify the signals of earthquakes.

But Tim Clements thinks it might be a tool to monitor one of the most precious resources in the world — water. A graduate student working in the lab of Assistant Professor of Earth and Planetary Sciences Marine Denolle, Clements is the lead author of a recent study that used seismic noise to measure the size and the water levels in underground aquifers in California.

The technique could even be used to track whether and how aquifers rebound following precipitation, and understand geological changes that might occur as water is pumped out. The study is described in a recently-published paper in Geophysical Research Letters. Clements explained:

Using those measurements, researchers were able to measure the water depth of the San Gabriel Valley aquifer, located just outside Los Angeles, to within a centimeter. Efforts to measure the size of the aquifer were limited by the existing seismic network, Clements said, and so were accurate only to about a kilometer. Denolle added:

Clements continued, saying:

That drought, Clements said, was one reason researchers chose to focus on the San Gabriel Valley:

The region is also already equipped with a network of seismographs, he said, making it relatively easy to obtain seismic noise data and use it to examine the aquifer. While the study wasn’t the first to hit upon the idea of using seismic noise to study groundwater, Denolle said earlier efforts were hampered because they relied on a signal that was relatively weak in comparison to environmental factors like temperature and pressure:

The system could also be a useful tool for anyone involved in water resource management, Clements said, because it can give them a moment-to-moment view of precisely what is happening in an underground aquifer:

Aside from providing groundwater measurements, the technique can also be used to monitor the health of an aquifer over time. Denolle said:

Going forward, Clements said, he plans to pursue ways to improve the resolution of the system at both the micro and macro levels.

Working in collaboration with faculty at Tufts University, he installed wells and seismometers on campus to track changes as groundwater is pumped to the surface to irrigate sports fields. Other efforts are focused on using the existing seismometer network in California to improve ways to measure the overall size of aquifers.

Provided by: Harvard University. [Note: Materials may be edited for content and length.]

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