Guoquan (Bob) Wang University of Houston Current Land Subsidence in the Houston Metropolitan Area, Texas, Derived from GPS Observations (1993-2012) Guoquan (Bob) Wang University of Houston With contributions from graduate students: Timothy J. Kearns, Jiangbo Yu, Linqiang Yang, Xueyi Jia, and Jianjun Jiang
Outline GPS Geodesy Infrastructure in the Houston area Public available GPS stations (Hardware) Stable Houston Reference Frame (SHRF) (Firmware) Single-receiver phase ambiguity resolved GIPSY PPP resolution (software) Current subsidence mapping (2005-2012) Scientific Questions: (1) Is there deep seated (or fault-controlled) subsidence in the Houston area? (2) When will the current subsidence stop?
Historic Subsidence in Houston 3 m within 30 years, 10 cm/year (USGS, Coplin and Galloway, 2009) (USGS, Kasmarek et al., 2009) 6 m Historic Subsidence in Houston USGS
Houston Ship Channel Area
Geodesy Infrastructure: Permanent GPS Stations Harris-Galveston Subsidence District (70+) Texas Department of Transportation 15+ 83 GPS +11 Extensometers City of Houston, others
HoustonNet NSF MRI: 40 GPS; UH: 10 GPS Subsidence, faulting, and salt dome uplift Hurricane intensity forecasting Civil engineering community---buildings, bridges, dams, sea walls
Geodesy Infrastructure: The Stable Houston Reference Frame Helmert Transformation 7 years: 2005-2012 Wang et al., 2013
14-Parameter Similarity Transformation Translation along the respective axis (in meters) Differential Scaling of the respective axis (ppb) Counterclockwise Rotations (in radians)
14-Transformation Parameters Unit IGS08 to SHRF t0 = 2012 IGS08 to NAD83(2011) t0 = 1997* Tx(t0) cm 0.00000 99.34300 Ty(t0) -190.33100 Tz(t0) -52.65500 Rx(t0) mas 25.91467 Ry(t0) 9.42645 Rz(t0) 11.59935 s(t0) ppb 1.71504 dTx cm/year -1.07250 0.07900 dTy -1.05876 -0.06000 dTz -3.54574 -0.13400 dRx mas/year 1.15720 0.06667 dRy -0.93885 -0.75744 dRz -0.33224 -0.05133 ds ppb/year 1.37220 -0.10201 NGS *Pearson and Snay (2013), Table 7
No-linear subsidence rate 18 Years Jersey Village Spatial and temporal variation of subsidence
Ground Deformation at Closely-Spaced (4 km) GPS Sites
Recent Subsidence Mapping (2005-2012) 85 years 6 m 83 GPS +11 Extensometers
Maximum subsidence rate <=2.5 cm/year < 5 mm/year 7 years: 2005-2012
Aquifer Profile: Chicot + Evangeline 3600 ft USGS
Subsidence---pumping (??%)+ faulting (??%) Question 1: Is there deep-seated (fault-controlled) subsidence in the Houston-Galveston area? Gulf Coast Geology and faults Subsidence vs. Faulting Subsidence---pumping (??%)+ faulting (??%) Ortega, 2013
USGS Borehole Extensometers Compaction meter USGS 13 extensometers at 11 sites 40 years: 1974—2013
Addicks Borehole Extensometer (-549 m)
Co-Located GPS and Extensometer Monitoring Site (ADKS) +15 years Wang et al., 2014
Wang et al., 2014 Journal of Surveying Engineering 18 years 40 years Drought of 2011 Drought of 2005 Conclusion: The compaction measurements from the long-term extensometers are reliable and the accuracy is about a few millimeters. Wang et al., 2014 Journal of Surveying Engineering
Co-located GPS and Extensometer Sites ADKS(-549 m) NETP (-591 m) LKHU (-661 m) 22 years Conclusion: Compacted aquifers are limited to above -600 m
Clear Lake—Jonson Space Center Sites Clear lake Deep Borehole (-936 m) Clear lake Shallow Borehole (-530 m) Jonson Space Center(-235 m) 50m 2.5 km 37 years Conclusion: No compaction below -530 m
-530 m USGS, 2009 Conclusion: Only partial of the Evangeline aquifer had been compacted!
Coastal Subsidence: Galveston vs. New Orleans 4 mm/year It appears no considerable tectonic subsidence occurs currently in the Houston-Galveston area.
UH Coastal Center “Vertical” GPS Array -1 ft -10 ft -20 ft -30 ft Borehole GPS
Question 2: When will the subsidence cease? 1978-1998 38 years Conclusion: It took 20 years (1978-1998) to halt the subsidence in the southeast part.
38 years Conclusion: 2005+20=2025
Summary The ground water and aquifer systems respond slowly to human actions. It took almost two decades (1980s and 1990s) to halt the subsidence in the south-east part of the Houston metropolitan area. Therefore, a long-term perspective is needed to manage groundwater resources and control land subsidence. The spatial and temporal variation of subsidence could be very considerable! subsidence=f(x,y,z t) The groundwater regulations implemented by the HGSD are very successful in reducing subsidence rate in the Houston area. Currently, there is no considerable deep-seated or fault-controlled subsidence in the Houston-Galveston area. Current aquifer compaction is limited to about -530m. Thank you!
Stable: v=0