Visualization of Active Faulting using 3-D GPR Data Recorded Across the Alpine Fault, New Zealand

Abstract

Three-dimensional (3-D) GPR data were acquired across braided river sediments cut by the Alpine Fault at Calf Paddock, New Zealand. We used 100 MHz antennas to obtain images of the subsurface to a depth of 15 m. Cross-sections and depth-converted time slices selected from the migrated data volume show both the structural contrast generated by recent offsets of the fault and the variable orientation of the dipping structures within the braided river deposits. A trace-correlation technique is used to generate dip and dip-direction attribute maps that allow us to visualize the 3-D orientation of the dipping structures. The attribute maps reveal at least 3 different reflection patterns and the presence of minor faulting away from the main fault. A correlation- based migration technique applied to a 2-D GPR profile resulted in the successful identification of the main fault and subsidiary faults at distances up to 50 m from the main fault.