Geomorphic, structural and chronological data are used to establish the late Quaternary paleoseismicity of the active dextral-oblique Northern Esk Fault in North Canterbury, New Zealand. Detailed field mapping of the preserved c. 35 km of surface traces between the Hurunui River and Ashley Head reveals variations in strike ranging from 005° to 057°. Along with kinematic data collected from fault plane striae and offset geomorphic markers along the length of the fault these variations are used to distinguish six structural subsections of the main trace, four dextral-reverse and two dextral-normal. Displacements of geomorphic markers such as minor streams and ridges are measured using differential GPS and rangefinder equipment to reveal lateral offsets ranging from 3.4 to 23.7 m and vertical offsets ranging from < 1 to 13.5 m. Characteristic single event displacements of c. 5 m and c. 2 m have been calculated for strike-slip and reverse sections respectively. The use of fault scaling relationships reveals an anomalously high displacement to surface rupture length ratio when compared to global data sets. Fault scaling relationships based on width limited ruptures and magnitude probabilities from point measurements of displacement imply earthquake magnitudes of Mw 7.0 to 7.5. Optically Stimulated Luminescence (OSL) ages from displaced Holocene alluvial terraces at the northern extent of the active trace along with OSL and radiocarbon samples of the central sections constrain the timing of the last two surface rupturing events (11.15 ±1.65 and 3.5 ± 2.8 ka) and suggest a recurrence interval of c. 5612 ± 445 years and late Quaternary reverse and dextral slip rates of c. 0.31 mm/yr and 0.82 mm/yr respectively. The results of this study show that the Northern Esk Fault accommodates an important component of the c. 0.7 – 2 mm/yr of unresolved strain across the plate boundary within the North Canterbury region and affirm the Esk Fault as a source of potentially damaging ground shaking in the Canterbury region.

Geomorphological and paleoseismic studies provide insight into the fault geometry and kinematics of a series of dextral northeast striking faults, including the Porters Pass, Hawdon, Bullock Hill, and Esk faults, in the South Island of New Zealand. These faults show post-glacial offsets that are significantly larger than predicted from co-seismic displacement - surface rupture length regressions derived from empirical relationships. Geomorphological mapping reveals slip rates as high as 9 mm/year for the Hawdon fault and Bullock Hill fault over an expected fault length of c. 140 km. Surface expressions of some parts of the studied faults are obscured by glacial gravels, indicating that blind faults are present in parts of the Sourthern Alps and may be the source for a component of a reported slip deficit in North Canterbury. Concluding from comparing scaling relationship results for the individual faults I hypothesize that the Porters Pass, Hawdon, Bullock Hill and Esk faults are segments of an incipient fault system that stretches from the western tip of the Porters Pass fault to the Hope fault, east of Hanmer Springs. Considering the location, similar strike and dextral deformation mode, I suggest that this 140 km long dextral strike-slip fault system marks the southernmost extension of the Marlborough Fault System resulting from the ongoing southward propagation of the Pacific-Australian plate boundary in New Zealand's South Island.