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

244 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 PATA Days 2024 K E Y W O R D S Paleoseismology, curved slickenlines, rupture direction, fault trenching (1) School of Geography, Environment and Earth Sciences, Victoria University of Wellington, New Zealand. (2) GNS Science, Lower Hutt, New Zealand. (3) Dept. of Earth & Planetary Sciences, University of California–Riverside, CA, USA. *Email: jesse@kearse.co.nz Jesse R. Kearse (1) Russ J. Van Dissen (2) Timothy A. Little (1) Nicolas C. Barth (3) UN-EARTHING FAULT-RUPTURE SLICKENLINES : TESTING A NEW METHOD TO EXCAVATE AND DOCUMENT PALEO SLICKENLINES ON ACTIVE FAULTS A B S T R A C T Earthquake rupture direction is known to influence the distribution of strong ground shaking in large earthquakes. A recent theory put forward by Kearse et al. (2019) suggests that the curvature of slickenlines preserved on fault surfaces can be used to infer the rupture direction of paleoearthquakes. We test this new theory by un-earthing slickenlines on a fault (Kekerengu Fault, New Zealand) with a known rupture propagation direction (northeast) during the 2016 Kaikōura earthquake. By trenching the Kekerengu Fault, we learn successful techniques to un-earth fault surfaces and document slickenlines. Slickenlines that were exhumed from 1-4 m below the ground surface record the same sense of convexity as those observed on scarps immediately following the Kaikōura earthquake, both of which indicate a northeast-directed rupture. Based on this work, we suggest that for shallow excavations the sense of convexity of curved slickenlines can be used to infer the direction of large paleoearthquake ruptures. I N T R O D U C T I O N During large magnitude earthquakes, rupture direction is known to influence the distribution of strong ground shaking, particularly in strike-slip earthquakes. Despite this, determining the rupture direction of paleoearthquakes is challenging, as there has been no reliable way to extract this information from the geological record. Recently, a new theoretical framework has been put forward by Kearse et al. (2019) and Kearse & Kaneko