The GNSS Geodetic Infrastructure and Current Ground Deformation in the Gulf of Mexico Region



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My study summarizes the current GNSS geodetic infrastructure in the Gulf of Mexico (GOM) region, which consists of three fundamental components: 1) an existing dense Continuously Operating Reference Station (CORS) network that is open to the public, 2) a stable regional reference frame that is tied to the International GNSS Service reference frame of 2008 (IGS08), and 3) sophisticated software packages for GNSS data post-processing that are freely available to the academic community. Among the current 780 CORS, there are approximately 350 stations that have a history longer than 5 years. The long-term accumulation of continuous GNSS observations makes it possible to establish a local reference frame for precisely and coherently delineating minor ground deformation over time and space. My study established a stable Gulf of Mexico reference frame using data up to 2014 (SGOMRF14). The GIPSY-OASIS software package (V6.3) was used to calculate daily positions of CORS in this study. GIPSY-OASIS employs the single-receiver phase ambiguity fixed Precise Point Positioning (PPP) method, which results in 2-3 mm horizontal and 7-8 mm vertical repeatability within the GOM region. SGOMRF14 is able to distinguish 0.2 mm/yr horizontal and 0.3 mm/yr vertical local ground deformation. The applications of the regional GNSS geodetic infrastructure are illustrated by depicting interplate and intraplate motions, monitoring the long-term ground deformation in large cities within the GOM region, studying deep-seated subsidence in the Houston metropolitan area and delineating the long-term absolute sea-level change along the GOM. GPS observations from the infrastructure indicate significant land subsidence in the coastal area of southeastern Louisiana, the greater Houston metropolitan area, and two cities located in Mexico (Aguascalientes and Mexico City). Significant spatial variation of subsidence rates was observed in both Mexico City and the Houston metropolitan area. GNSS stations in southeastern Louisiana indicate minor (< 6.0 mm/yr) but consistent subsidence over time and space. Combined with extensometer data, my study has demonstrated that recent subsidence (1993-2012) in the Houston-Galveston area was dominated by compaction within the top 600 m of sediment. Deep-seated subsidence is not likely occurring in the Houston-Galveston area. The dispersion of the sea-level rise rates, measured by seven tide gauges located along the Gulf Coast, has been reduced from 2.66 mm/yr to 0.63 mm/yr after local land vertical motion corrections by the GNSS geodetic infrastructure. My study indicates that the average absolute sea-level rise along the GOM coast is 1.8 mm/yr.



Subsidence, GNSS, Reference frames, Sea level rise, Groundwater withdrawl


Portions of this document appear in: Yu, J., and G. Wang. "Introduction to the GNSS geodetic infrastructure in the Gulf of Mexico Region." Survey Review 49, no. 352 (2017): 51-65. And in: Yang, Linqiang, Guoquan Wang, Yan Bao, Timothy J. Kearns, and Jiangbo Yu. "Comparisons of ground-based and building-based CORS: A case study in the region of Puerto Rico and the Virgin Islands." Journal of Surveying Engineering 142, no. 3 (2015): 05015006. And in: Yu, Jiangbo, and Guoquan Wang. "GPS-derived ground deformation (2005-2014) within the Gulf of Mexico region referred to a stable Gulf of Mexico reference frame." Natural Hazards & Earth System Sciences 16, no. 7 (2016). And in: Yu, Jiangbo, Guoquan Wang, Timothy J. Kearns, and Linqiang Yang. "Is there deep-seated subsidence in the Houston-Galveston area?." International Journal of Geophysics 2014 (2014). And in: Wang, Guoquan, Jiangbo Yu, Timothy J. Kearns, and Jesse Ortega. "Assessing the accuracy of long-term subsidence derived from borehole extensometer data using GPS observations: Case study in Houston, Texas." Journal of surveying engineering 140, no. 3 (2014): 05014001.