GEOPHYSICAL STUDY OF THE NEEDVILLE AND ARCOLA FAULTS IN FORT BEND COUNTY, TEXAS

Several active faults are reported from southeast Texas. These faults have been studied in great detail in Harris County, but little work has been done in Fort Bend County where there are at least four known fault systems. These are the Long Point, Needville, Arcola, and Addicks fault systems. This study focuses on the Needville and Arcola fault systems in an effort to determine the continuity and displacement along these two fault systems. As sediments around these faults move slowly, displacements can be unnoticeable. The purpose of this study is to build on the previous work done on faults in Fort Bend with the use of the latest geophysical tools to better identify and understand the faulting mechanisms. The technologies that are used include Light Detection and Ranging (LiDAR), aerial photographs, Ground Penetrating Radar (GPR), Seismic, Well Logs, Global Positioning System (GPS), and Gravity. LiDAR results produced high resolution surface models of the faults and revealed three new faults. Seismic, GPR, and Gravity surveys were conducted along a 960 meter profile with utilization of a 15,000lb vibroseis and 192 geophones, GPR system with 100 and 400 MHz antennas, and a CG-5 gravimeter. The seismic and GPR have both produced sections that clearly display faulting, as well as there is a gravity variation across fault. Integration of these geophysical techniques has produced cross sections of the faults that are helping in the understanding of the mechanisms driving faulting in this region. The collected well logs, seismic, and GPR data allowed for the ability to calculate throws ranging from inches to 300 feet along with strike and true dip of the faults. A 3D model of the area has been produced that integrates a DEM produced by LiDAR for the ground surface, GPR extended from the DEM to a depth where seismic is then extended to depth, and over 200 correlated well logs that have produced multiple structure layers and fault planes. This study provides greater knowledge for the area as it continues to urbanize and produce hydrocarbons. This may lead to better city planning and engineering to avoid possible hazards, and better visualize hydrocarbon traps. The knowledge gained in this study will help us to better understand geological events that occur in the passive margin along the Gulf Coast and better predict the future of coastal areas.