NSF Grant Supports Measurement of "Heartbeat" of the Ground Underlying Houston

NSF Grant Supports Measurement of "Heartbeat" of the Ground Underlying Houston
GPS Network To Provide Continuous, High-Precision Measurements in Real Time

Gabriel Saenz
Gabriel Saenz, a UH graduate student in geology, installs the first HoustonNET GPS station in front of the Harris-Galveston Subsidence District headquarters. HoustonNET will have 40 real-time permanent GPS stations across the Great Houston Metropolitan area.
Most Houstonians are unaware how much the ground in this city moves beneath their feet. A two-year, $401,000 National Science Foundation (NSF) grant will establish a network of continuously monitoring, high-precision Global Positioning System (GPS) stations to provide researchers with better information about the city’s natural hazards. The project includes $172,000 in matching support from the University of Houston.

“The GPS observational network, called HoustonNET, will provide the infrastructure for a broad range of natural hazards research, covering topics such as subsidence, active faults, flooding, salt dome movement, and hurricane intensity forecasting,” said Guoquan ‘Bob’ Wang, an assistant professor of geophysics, who joined UH’s Department of Earth and Atmospheric Sciences in 2011. “We will also use the data to look at urban heat island effect, which is the condition when a metropolitan area is significantly warmer than its surrounding rural areas due to human activities.”

HoustonNET will consist of 40 GPS stations covering about 10,000 square miles of the Greater Houston Metropolitan area. The measuring stations, positioned across the city at distances of 10 to 20 miles, will continuously record data from GPS satellites. With this data, precise calculations can be made to show how the various sites are moving with respect to one another.

Several UH departments are collaborating on HoustonNET with co-investigators from the Department of Earth and Atmospheric Sciences, the Department of Civil and Environmental Engineering, and the Department of Engineering Technology. The leadership team includes professors Wang, Ramesh Shrestha, Thomas Hsu, Shuhab Khan, Barry Lefer, Paul Mann, William Carter, Yi-Lung Mo, Hassan Moghaddam, Craig Glennie, and Hyongki Lee.

“As cities grow and get denser, the potential impacts of natural hazards, such as flooding, active faulting, and widespread surface subsidence, increase significantly,” said Wang, the project’s principal investigator. “HoustonNET’s long-term, continuous measurement of horizontal and vertical ground surface motions will help us better understand, monitor, forecast, warn, and minimize the impacts of these natural hazards.”

The team will integrate its new data with ongoing efforts by county, state and federal agencies on precise measurements of land subsidence linked to water pumping. The team is also forming collaborations with Houston-based oil exploration and data companies to examine seismic reflection and well data from areas of active faulting and land subsidence.

Houston experiences ground instability in several ways, from fault movements that crack sidewalks and building foundations, to changes in the ground surface during extreme droughts as in the summer of 2011 or during extreme flooding caused by hurricanes and storms. Other changes include accelerated subsidence caused by pumping oil and water out of the ground, the swelling and subsidence of salt domes beneath the surface, and the loading effect of high-rise buildings and construction on the underlying fine-grained soils. Several large salt domes are found within the city limits and will be closely monitored from GPS data and subsurface data from the oil industry.

A significant part of the project will involve training of master’s and Ph.D. students at UH. Since 2005, the UH Department of Earth and Atmospheric Sciences has awarded four post-graduate degrees in studies of active faulting and subsidence in the Houston area. The new funding will provide support for two graduate students to acquire and analyze the new GPS data.

HoustonNET will also provide real-time atmospheric water vapor measurements by atmospheric scientists from the UH Department of Earth and Atmospheric Sciences. “These measurements will allow advanced atmospheric study and can be used to improve regional weather forecasting and hurricane intensity forecasting,” said Wang, who is a current recipient of an NSF CAREER Award.

HoustonNet will be operated by UH in collaboration with the Harris-Galveston Subsidence District, Fort Bend Subsidence District, and U.S. Geological Survey (USGS). HoustonNET sites will be located at existing GPS sites operated by the subsidence districts, extensometer sites operated by USGS, and weather and environmental towers operated by UH.

“Once all the stations are installed and operational, the data will not only impact scientific research. The network will provide high-quality GPS and weather data to the public, local governments and public service agencies,” Wang said. “Our goal is to make all results available to the public in real time via the Internet just like our department is doing with Houston air quality information.”

- Kathy Major, College of Natural Sciences and Mathematics