Han published his Master's Thesis in 2013 and reported that active faults in Houston area are an ongoing problem, and this continues to cause damage to the local roads and infrastructures. Within the last 3 years, residents in the Woodlands area have reported increasing property damage from faulting caused by the Hockley Fault System. Rapid slip rates and the potential damages portray the need of further study.
The objective of this study is to gain greater insights into the Hockley Fault and to increase the available information of active faults. The objectives were achieved in part through acquisition of new 2-D shallow seismic and gravity data in the vicinity of the main fault scarp. This second part of the study focused on the use of three generations of LiDAR data for mapping the terminal segment of the Hockley Fault and for calculating the rate of fault displacement as well as utilizing GPS data to further test the fault activity.
The author concluded that:
1. The 2-D shallow seismic technique is a powerful tool in the detection of the fault structures in the subsurface; seven faults were detected in the study area. Fault numbers 1, 2, 3, 4, 5, 6, and 7 are possibly related to salt diapirism. Contacts for several formations in the subsurface were identified. These formations generally show a flat trend in the upper 500 m and are deformed below 500 m by salt activity. Fault number 4 is interpreted as the Hockley Fault, which intersects with another fault that is dipping in the opposite direction. The Hockley Fault is dipping toward the Gulf Coast with an estimated angle of 60 degrees. A lot of cracks on the feeder road of Highway 290 have been observed in the field that were likely caused by those normal listric faults in the subsurface. Further careful observation of potential activity of fault numbers 1, 2, 5, 6, and 7 are needed to prevent any potential damages.
2. Gravity data shows a fault signature as an S-shape curve in the study area. Two areas with gravity anomalies are observed on each side of the Hockley Fault; this may reflect the lithologic changes and fault structures in the subsurface.
3. LiDAR hillshade technique proved to be the most effective way of mapping surface faults and it shows great advantage in fault scarp detection. The result of the hillshade technique suggested that the main Hockley Fault segment is about 12 km long, extending from northwest to southeast and spreading out into many small faults near the Tomball salt dome.
4. GPS data suggests that a relatively rapid subsidence has occurred on both the upthrown and down thrown sides of some segments of the Hockley Fault.
5. Further mapping at the very end of the Hockley Fault System in Woodlands, Texas, was carried out by detection of the fault scarp that was confirmed by hill shade. Three generations of LiDAR data were used to estimate the slip rate along this segment of the Hockley Fault. Generally speaking, the rate of the fault movement shows a decrease, and the fault movement rate falls from 2.58cm/year (2001–1996) to 2.14
cm/year (2008–2001).
6. This study combined different data sets: 2-D shallow seismic, gravity, and LiDAR and GPS data over a segment of the Hockley Fault, and six new faults were identified in the vicinity of the Hockley Fault zone. The boundaries of different formations and fault structures and potential salt dome locations were also identified.
7. A longer period of observation of the Hockley Fault is recommended to monitor the movement of the fault and other normal listric faults to prevent the potential damages to the buildings, neighborhoods, and so forth.
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