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

74 PATA Days 2024 1 2 T H I N T E R N AT I O N A L I N Q U A M E E T I N G O N PA L E O S E I S M O L O G Y , A C T I V E T E C T O N I C S A N D A R C H A E O S E I S M O L O G Y ( PATA ) , O C T O B E R 6 T H - 1 1 T H , 2 0 2 4 , L O S A N D E S , C H I L E K E Y W O R D S Paleoseismology, curved slickenline, rupture directivity, earthquake gate, Alpine Fault (1) Dept. of Earth & Planetary Sciences, University of California-Riverside, CA, USA. (2) School of Geography, Environment and Earth Sciences, Victoria University ofWellington, New Zealand. (3) GNS Science, Lower Hutt, New Zealand. *Email: nic.barth@ucr.edu Nicolas C. Barth (1) Jesse R. Kearse (2) Tim A. Little (2) Russ J. Van Dissen (3) CURVED SLICKENLINES RECORD RUPTURE DIRECTIVITY OF PALEOEARTHQUAKES ON THE ALPINE FAULT, NEW ZEALAND A B S T R A C T We present results of the first attempt to observe and exhume curved slickenlines associated with paleo-surface rupture on principal slip surfaces of the Alpine Fault, New Zealand's ~30 mmlyr continental transform plate boundary. We focused our efforts on three sites (south to north: Hokuri Creek, Martyr River, Chasm Creek) that span a known "earthquake gate" region to contribute rupture directivity data to the fault's spatiotemporally-rich paleoseismic record. At Hokuri and Martyr we observed both senses of curved slickenlines on and adjacent to principal slip surfaces indicating evidence far past ruptures from the northeast and southwest of these locations; at Martyr relationships suggestthe most recent event (inferred to correlate to 1717 AD) ruptured from the southwest. We conclude that curved slickenlines are a viable wayto enrich paleoseismic records. We highlight the potential that curved slickenlines from multiple ruptures can be preserved and acknowledge the challenge in dating these features.