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Tech to Study How Fault Zones Control Groundwater Flow

SOCORRO, NM February 24, 2016 – Three professors in New Mexico Tech’s Department of Earth and Environmental Science recently landed a $500,000 grant from the National Science Foundation to study how faults control fluid flow. 

Drs. Glenn Spinelli, Peter Mozley, and John Wilson will address the difficult question of the role that natural cements play in controlling the ease with which fluids pass through geologic faults.

  fault-zone-field-work
 

Geologists examine strongly cemented fault west of Rio Rancho, N.M. Such faults have a major impact on groundwater levels in the Rio Grande aquifer system. The new NSF-funded project will examine an exposed fault near Socorro.

 

Geologic faults usually make the news only when they have produced damaging earthquakes. However, faults also quietly have an important impact on society that most people never think about – they control the flow of groundwater and petroleum in aquifers and oil fields. 

In fact, a fault acting as a barrier for fluids can make the difference between a productive water or oil well and a terrible one.  This is true for the Rio Grande aquifer system, in which groundwater levels can change tremendously as fault zones are crossed. 

The cements are composed of minerals precipitated from groundwater over thousands of years or more.  As the minerals precipitate they fill open spaces (pores) in the rock, clogging them up (like the build-up of plaque in arteries), making it difficult for fluids to flow.

However, determining the distribution of fault-zone cements is difficult. As a result, fault-zone cementation is typically not accounted for in estimates of the impact of faults on fluid flow. In the New Mexico Tech study, the professors and their students will take advantage of unique electrical properties of natural cements – their ability to conduct electricity differs from the surrounding non-cemented rock.

They will use electrical resistivity tomography to map the 3-D distribution of cements in an exceptionally well-exposed fault zone a few miles north of Socorro.  Then, they will directly measure the impact of the cements on groundwater flow by drawing water from wells adjacent to the fault. 

“It’s exciting, because our results should help us understand how faults control fluid flow,” Spinelli said.  “Whether faults act as barriers or conduits for fluid is important for a lot of issues, like groundwater supply, petroleum migration, contaminant transport, and underground waste storage.”

The project will support three graduate students and several undergraduates. The project will begin during the summer of 2016 and continue for three years.

– NMT –