Subsidence and Faulting in Houston
Khan et al., 2022
Introduction
The fourth largest city in the country, Houston, Texas, has experienced some of the most considerable subsidence of any megacity in the USA, losing over 3 m in elevation in certain areas since 1917. Excessive groundwater withdrawal and sediment compaction are the main drivers of subsidence. The northern Gulf of Mexico is also home to numerous faults and salt domes, and many of the faults are still active. So, the surface deformation in this region may not be purely anthropogenic in origin, with geologic elements, such as faults and salt domes may be contributing.
Figure 1. Map of study area showing InSAR coverage area, locations of 71,170 water wells, and 5948 oil/gas wells that were used for optimized hot spot analysis
Methodology
Khan et al. (2022) processed Sentinel-1 InSAR data utilizing the Small Baseline Subset (SBAS) interferometry technique from January 2016 to December 2020 to estimate the subsidence. The animation (Fig. 2) was created using line of sight (LOS) displacement data at various dates. This study applied emerging hot spot analysis to find the spatiotemporal trend in the subsidence of the greater Houston area. Lidar datasets collected in 2018 and 2019 are used to update this region's faults map (Fig. 3).
Results and Analysis
Persistent subsidence is observed in many parts of the area. Suburbs and small towns adjacent to Houston show significant negative LOS displacement. For example, Katy, Spring, Woodlands. Several other small towns further away to the south, southeast, northeast, and northwest show similar trends.
Figure 2: Surface Deformation Analysis of the Houston Area Using Time Series Interferometry
Emerging hot spot analyses shows four statistically significant clusters of subsidence. A large area encircling Houston from southeast to west to north depicts historical, consecutive, and intensifying hot spots. Similar clusters are in the east around Mont Belvieu, northwest around College Station, and south around Wharton. There are a few additional clusters in small rural communities.
LOS displacement time series for downthrown and upthrown blocks indicate that the Long Point Fault seems to be inactive (2016-2020). At the same time, faults located in subsiding areas in the northwest and north are active in this time period.
Figure. 3 Emerging hot spot results for subsidence and updated fault map of Houston and surrounding areas
