Result
Figure.13. Horizontal velocity vectors referenced to NAD83 indicates approximate in north and north-west direction and in a about 2-4 mm/year. However this results shows relatively uneven distribution of the vectors under effect of the movement in reference frame.
Figure.13. Horizontal velocity vectors referenced to UTEX shows the velocity vectors of those stations nearby UTEX are very subtle to none. The vectors shows the relative movement is in northeast direction in a rate about 1~2 mm/year and the difference of velocity vectors between SPBH and CSTA can indicate the movement of the fault.
Figure.14. Vertical velocity vectors referenced to NAD83 indicates the overall subsidence in a rate about 2-8mm/year; however, only station TSFT shows the uplift
Figure.15. Vertical velocity vectors indicates the overall subtle subsidence referenced to UTEX in a rate about 1-2 mm/year
Three years groundwater data is also used in this study to examine the subsidence and compare with GPS results. In Figure 16 it can be seen that there are some wells show the groundwater level rising; however GPS data demonstrates the overall subsidence in this area (Fig.14.). This is because although the groundwater level is rising it is still beneath preconsolidation head (Fig.17.), which is about -30~-40m and since groundwater within the Chicot and Evangeline aquifers are hydraulically connected to each other the preconsolidation head are also identical (Kearns et al., 2015) and subsidence will continue to occur as long as the groundwater head stays below the local preconsolidation head (Poland and Davis 1969).
Figure.16. Groundwater data used in this study, blue indicates the water level falling and orange indicates the rising and the size is proportional to the amount of the water level change although the GPS data indicates general the subsidence in whole area.
Figure.17. Groundwater head depth and velocity vectors of GPS referenced to NAD83, blue indicates the water level falling and orange indicates the rising and the size is proportional to the amount of the depth of preconsolidation head. The average depth of the Chicot and Evangeline aquifers is -30~-40m and the average depth of Evangeline aquifer is -70m. The area with more subsidence is also the area with the falling water level or rising water level, but still lower than average depth.
Figure.18. Comparison of real-time groundwater and GPS movement, red is the groundwater in the depth about 5m and blue is the groundwater in the depth about 100m so red signal is more sensitive to the seasonal change.
Figure.19. Comparison of real-time groundwater and GPS movement, black is the groundwater in the depth about 5m with time shift and blue is the groundwater in the depth 100m. Although not very well it shows a little seasonal correlation between GPS and groundwater data and this will be used to do the filtering in the future.
Figure.20. DEM generated from point clouds of six TLS scans. The result shows the affects of the interpolation and thus the "bull eye" structure. The fault trace can be seen in the DEM but is not continuous so the further filter may needed to improve the result.