TWO DECADES GPS OBSERVATIONS IN THE GREATER HOUSTON AREA: A TESTIMONY TO THE COMPLEXITY OF LAND SUBSIDENCE AND UPLIFT

The greater Houston, Texas, area has been suffering from substantial land subsidence problem for almost one century. GPS techniques have been applied to study land subsidence in the greater Houston area for over two decades (1993-2016). A dense continuous GPS network for subsidence study has been established since 1993 by a joint effort of the Harris-Galveston Subsidence District (HGSD), the Texas Department of Transportation (TxDOT), the National Geodetic Survey (NGS), the University of Houston, Houston City, and several other local agencies. Currently, there are over 180 public-available permanent GPS stations in the greater Houston area. Among them, over 160 GPS stations have an observational history of over two years as of the end of 2016. This presentation will introduce current geodetic infrastructure in the greater Houston area and ground deformation time series (faulting, subsidence and uplift) recorded by GPS during the past two decades. Interaction of subsidence and uplift with groundwater level changes will be investigated. The infrastructure comprises three components: the permanent GPS network, the Stable Houston Reference Frame (SHRF), and sophisticated software packages for GPS data processing. The greater Houston area described in this investigation comprises Harris, Fort Bend, Brazoria, and Galveston Counties and adjacent portions of the surrounding counties: Chambers, Liberty, Montgomery, and Waller Counties. This area covers an area of approximately 150 × 150 km and has a population of over 6 million.