Proceedings of the 12th International INQUA meeting on paleoseismology, active tectonic and archaeoseismology

78 PATA Days 2024 Fig. 3: (A) Slope-shaded lidar hillshade of Martyr River site with fault traces in black. (B) Structure- from-Motion (SfM) model orthographic projection of subvertical principal slip surface with curved slickenline locations. (C) Population of groove and gouge type slickenlines indicating convex-up slip path on the principal slip surface. (D) Gouge- hosted convex-down curved slickenline populations located <10 cm fromprincipal slip surface. C O N C L U S I O N S We conclude that documenting curved slickenlines is a viable approach to enrich paleoseismic records of active faults, including those lacking historical surface rupture, by contributing evidence of paleoearthquake rupture direction. Beyond the sense of curvature and orientation, recording slickenline length, shape, type, context, and dating are valuable. Curved slickenlines from multiple surface ruptures can be preserved ata single site and on a single principal slip surface allowing rich paleoseismic data to be collected; this does however present a challenge in dating populations of curved slickenlines and correlating them to known paleoearthquakes. We report the first curved slickenlines identified on the Alpine Fault; these indicate that past surface ruptures of the Alpine Fault have initiated from both north and south of Martyr River and Hokuri Creek lf the earthquake gate occurs at the major change in kinematics at the Martyr River, then our results indicate the gate allows multi section rupture fromboth the southwest and northeast. We tentatively suggest that the most recent multi-section (~Mw 8) 1717 AD rupture of the Alpine Fault initiated from a location south of the earthquake gate (i.e. south of Martyr River). A C K N O W L E D G E M E N T S We acknowledge support from the Royal Society of New Zealand Marsden Fund (20-GNS-006; PI: R. Van Dissen; additional collaborators: Y. Kaneko, J. Howarth, C. Orchiston). Fieldwork was carried out under authority granted by the NZ Department of Conservation (53621-GEO, PI: N. Barth).