Preliminary evaluation of tectonic geomorphological signals within the Hamilton Basin

Abstract

Over the past year several fault traces have been discovered within the Hamilton Basin, prompting a need for further investigation for tectonic evidence in the basin in order to re asses seismic hazards of the basin. Examination of the most recently discovered fault revealed the trace cross cuts the 20,000 ka Hinuera Formation, indicating that the faults within the Basin are active and could potentially experience another seismic event. However, more information is needed to determine the rate of occurrence and potential magnitude of an event. LiDAR and geomorphic data indicates there are potentially up to ten more traces within the Hamilton Basin, but they have yet to be confirmed through geomorphical ground-truth mapping. Both the known fault traces and the potential traces are dominantly NE oriented and appear to be influenced by the surrounding fault systems, such as the Waipa Fault. A large basement depression located in the far northern area of the Hamilton Basin as revealed by seismic line and gravitational data indicates that extensional movement may be related to the faults. To better understand the risk and hazard potential of a seismic event, extensive study and information about the basement terrane and surrounding faults, such as the Waipa Fault, needs to be gathered. It is possible that the fault traces within Hamilton are transtensional splays that have formed to accommodate movement and space between the major fault systems. My project will be examining the inferred fault traces within the Hamilton Basin, as indicated by the geomorphology, seismic line data, existing borehole data, and geological and geomorphical ground-truth mapping. For this the history of the surrounding fault lines, such as their total offset and rate of occurrence, will be investigated in order to understand the behavior of the faults within the Hamilton Basin and the potential hazards they can cause.