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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. - PowerPoint PPT Presentation
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Current Land Subsidence in the Houston Metropolitan Area, Texas, Derived from
GPS Observations (1993-2012)
Guoquan (Bob) WangUniversity 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?
(USGS, Kasmarek et al., 2009)
(USGS, Coplin and Galloway, 2009)
Historic Subsidence in Houston
3 m within 30 years, 10 cm/year
6 m
USGS
Houston Ship Channel Area
Geodesy Infrastructure: Permanent GPS Stations
Harris-Galveston Subsidence District (70+)
Texas Department of Transportation 15+
City of Houston, others
83 GPS +11 Extensometers
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
7 years: 2005-2012
Helmert Transformation
Wang et al., 2013
14-Parameter Similarity Transformation
8
(1) Translation along the respective axis (in meters)
(2) Differential Scaling of the respective axis (ppb)
(3) Counterclockwise Rotations (in radians)
14-Transformation Parameters
9
Transformation Parameter UnitIGS08 to SHRFt0 = 2012
IGS08 to NAD83(2011)t0 = 1997*
Tx(t0) cm 0.00000 99.34300Ty(t0) cm 0.00000 -190.33100Tz(t0) cm 0.00000 -52.65500Rx(t0) mas 0.00000 25.91467Ry(t0) mas 0.00000 9.42645Rz(t0) mas 0.00000 11.59935s(t0) ppb 0.00000 1.71504dTx cm/year -1.07250 0.07900dTy cm/year -1.05876 -0.06000dTz cm/year -3.54574 -0.13400dRx mas/year 1.15720 0.06667dRy mas/year -0.93885 -0.75744dRz mas/year -0.33224 -0.05133ds ppb/year 1.37220 -0.10201
*Pearson and Snay (2013), Table 7
NGS
No-linear subsidence rate
Jersey Village
18 Years
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
USGS3600 ft
Subsidence---pumping (??%)+ faulting (??%)
Gulf Coast Geology and faults
Ortega, 2013
Subsidence vs. Faulting
Question 1: Is there deep-seated (fault-controlled) subsidence in the Houston-Galveston area?
USGS Borehole Extensometers
13 extensometers at 11 sites 40 years: 1974—2013
USGS
Compaction meter
Addicks Borehole Extensometer (-549 m)
Co-Located GPS and Extensometer Monitoring Site (ADKS)
Wang et al., 2014
+15 years
Wang et al., 2014Journal of Surveying Engineering
Conclusion: The compaction measurements from the long-term extensometers are reliable and the accuracy is about a few millimeters.
Drought of 2005
Drought of 2011
18 years
40 years
Co-located GPS and Extensometer Sites
Conclusion: Compacted aquifers are limited to above -600 m
ADKS(-549 m) NETP (-591 m) LKHU (-661 m)
22 years
Clear Lake—Jonson Space Center Sites
Conclusion: No compaction below -530 m
Clear lake Deep Borehole (-936 m) Clear lake Shallow Borehole (-530 m) Jonson Space Center(-235 m)
50m 2.5 km
37 years
-530 m
Conclusion: Only partial of the Evangeline aquifer had been compacted!
USGS, 2009
Coastal Subsidence: Galveston vs. New Orleans
It appears no considerable tectonic subsidence occurs currently in the Houston-Galveston area.
4 mm/year
UH Coastal Center “Vertical” GPS Array
-30 ft-20 ft-10 ft -1 ft
Borehole GPS
Question 2: When will the subsidence cease?
Conclusion: It took 20 years (1978-1998) to halt the subsidence in the southeast part.
1978-1998
38 years
Conclusion: 2005+20=2025
38 years
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