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

396 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 intracontinental regions, earthquake behavior, Paleoseismic data, lacustrine environments (1) Université Paris cité, institut de Physique du Globe de Paris, CNRS, Paris, France. (2) Université de Savoie, Laboratoire Environnement Dynamiques et Territoire de Montagne, CNRS, Le Bourget du Lac, France. (3) Korea Institute of Geosciences and Mineral Resources, Daejeon, South Korea. (4) Institute of astronomy and geophysics, Ulaanbaatar, Mongolia. *Email: pinzonmatapi@ipgp.fr Nicolas Pinzon Matapi (1) Yann Klinger (1) Pierre Sabatier (2) Edward Duarte (2) Jin-hyuck Choi (3) Taehyung Kim (3) Baataraa Ga (4) POTENTIAL RECORD OF LARGE EARTHQUAKES FROM LAKE SEDIMENTARY ARCHIVES ALONG THE BULNAY FAULT (NORTHWEST MONGOLIA) A B S T R A C T On July 1905, two M~8 earthquakes occurred 14 days apart along the Bulnay Fault system, in northwestern Mongolia. These seismic events are among the largest recorded earthquakes in intracontinental regions. However, our current understanding of the earthquake behavior of the Bulnay Fault is quite limited due to the scarcity of paleoseismic data. Additionally, the geographic and climatic conditions of the region play a major key in permafrost development, posing challenges in the excavation of fault-trenches and causing cryoturbation. Lacustrine environments, conversely, are isolated depositional systems that minimize the influence of external factors and provide high temporal resolution with continuous sedimentation. Here, we present our findings on earthquake- triggered turbidites of eight sedimentary cores collected from three lakes around the Bulnay Fault. These cores were analyzed using X-ray tomography, X-ray fluorescence, and hyperspectral imaging. Based on this approach we aim to better understand the temporal occurrence of large earthquakes deep within continental interiors. I N T R O D U C T I O N In 1905 two major strike-slip earthquakes occurred in the northern part of the Hangay massif, north-western Mongolia (Figure 1). First, the magnitude MW 8.0 Tsetserleg earthquake occurred on 9 July at 9:40 (UT time). 14 days later, on 23 July at 2:46 am, the Bulnay earthquake occurred along the left-lateral, strike-slip Bulnay fault, at the intersection with the right-lateral, strike-slip Teregtyin fault ( Baljyniiam et al., 1993). Seismic inversion of body waves, performed by Schlupp & Cisternas (2007), yielded magnitudes ranging between 8.3 and 8.5. These observations make the Bulnay earthquake one of the largest